/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.lang3.time;

import java.text.ParseException;
import java.text.ParsePosition;
import java.util.Calendar;
import java.util.Date;
import java.util.Iterator;
import java.util.Locale;
import java.util.NoSuchElementException;
import java.util.TimeZone;
import java.util.concurrent.TimeUnit;

import org.apache.commons.lang3.LocaleUtils;
import org.apache.commons.lang3.Validate;

/**
 * <p>
 * A suite of utilities surrounding the use of the {@link java.util.Calendar}
 * and {@link java.util.Date} object.
 * </p>
 *
 * <p>
 * DateUtils contains a lot of common methods considering manipulations of Dates
 * or Calendars. Some methods require some extra explanation. The truncate,
 * ceiling and round methods could be considered the Math.floor(), Math.ceil()
 * or Math.round versions for dates This way date-fields will be ignored in
 * bottom-up order. As a complement to these methods we've introduced some
 * fragment-methods. With these methods the Date-fields will be ignored in
 * top-down order. Since a date without a year is not a valid date, you have to
 * decide in what kind of date-field you want your result, for instance
 * milliseconds or days.
 * </p>
 * <p>
 * Several methods are provided for adding to {@code Date} objects, of the form
 * {@code addXXX(Date date, int amount)}. It is important to note these methods
 * use a {@code Calendar} internally (with default time zone and locale) and may
 * be affected by changes to daylight saving time (DST).
 * </p>
 *
 * @since 2.0
 */
public class DateUtils {

	/**
	 * Number of milliseconds in a standard second.
	 * 
	 * @since 2.1
	 */
	public static final long MILLIS_PER_SECOND = 1000;
	/**
	 * Number of milliseconds in a standard minute.
	 * 
	 * @since 2.1
	 */
	public static final long MILLIS_PER_MINUTE = 60 * MILLIS_PER_SECOND;
	/**
	 * Number of milliseconds in a standard hour.
	 * 
	 * @since 2.1
	 */
	public static final long MILLIS_PER_HOUR = 60 * MILLIS_PER_MINUTE;
	/**
	 * Number of milliseconds in a standard day.
	 * 
	 * @since 2.1
	 */
	public static final long MILLIS_PER_DAY = 24 * MILLIS_PER_HOUR;

	/**
	 * This is half a month, so this represents whether a date is in the top or
	 * bottom half of the month.
	 */
	public static final int SEMI_MONTH = 1001;

	private static final int[][] fields = { { Calendar.MILLISECOND }, { Calendar.SECOND }, { Calendar.MINUTE },
			{ Calendar.HOUR_OF_DAY, Calendar.HOUR }, { Calendar.DATE, Calendar.DAY_OF_MONTH, Calendar.AM_PM
			/* Calendar.DAY_OF_YEAR, Calendar.DAY_OF_WEEK, Calendar.DAY_OF_WEEK_IN_MONTH */
			}, { Calendar.MONTH, SEMI_MONTH }, { Calendar.YEAR }, { Calendar.ERA } };

	/**
	 * A week range, starting on Sunday.
	 */
	public static final int RANGE_WEEK_SUNDAY = 1;
	/**
	 * A week range, starting on Monday.
	 */
	public static final int RANGE_WEEK_MONDAY = 2;
	/**
	 * A week range, starting on the day focused.
	 */
	public static final int RANGE_WEEK_RELATIVE = 3;
	/**
	 * A week range, centered around the day focused.
	 */
	public static final int RANGE_WEEK_CENTER = 4;
	/**
	 * A month range, the week starting on Sunday.
	 */
	public static final int RANGE_MONTH_SUNDAY = 5;
	/**
	 * A month range, the week starting on Monday.
	 */
	public static final int RANGE_MONTH_MONDAY = 6;

	/**
	 * Calendar modification types.
	 */
	private enum ModifyType {
		/**
		 * Truncation.
		 */
		TRUNCATE,

		/**
		 * Rounding.
		 */
		ROUND,

		/**
		 * Ceiling.
		 */
		CEILING
	}

	/**
	 * <p>
	 * {@code DateUtils} instances should NOT be constructed in standard
	 * programming. Instead, the static methods on the class should be used, such as
	 * {@code DateUtils.parseDate(str);}.
	 * </p>
	 *
	 * <p>
	 * This constructor is public to permit tools that require a JavaBean instance
	 * to operate.
	 * </p>
	 */
	public DateUtils() {
	}

	// -----------------------------------------------------------------------
	/**
	 * <p>
	 * Checks if two date objects are on the same day ignoring time.
	 * </p>
	 *
	 * <p>
	 * 28 Mar 2002 13:45 and 28 Mar 2002 06:01 would return true. 28 Mar 2002 13:45
	 * and 12 Mar 2002 13:45 would return false.
	 * </p>
	 *
	 * @param date1 the first date, not altered, not null
	 * @param date2 the second date, not altered, not null
	 * @return true if they represent the same day
	 * @throws IllegalArgumentException if either date is {@code null}
	 * @since 2.1
	 */
	public static boolean isSameDay(final Date date1, final Date date2) {
		if (date1 == null || date2 == null) {
			throw nullDateIllegalArgumentException();
		}
		final Calendar cal1 = Calendar.getInstance();
		cal1.setTime(date1);
		final Calendar cal2 = Calendar.getInstance();
		cal2.setTime(date2);
		return isSameDay(cal1, cal2);
	}

	/**
	 * <p>
	 * Checks if two calendar objects are on the same day ignoring time.
	 * </p>
	 *
	 * <p>
	 * 28 Mar 2002 13:45 and 28 Mar 2002 06:01 would return true. 28 Mar 2002 13:45
	 * and 12 Mar 2002 13:45 would return false.
	 * </p>
	 *
	 * @param cal1 the first calendar, not altered, not null
	 * @param cal2 the second calendar, not altered, not null
	 * @return true if they represent the same day
	 * @throws IllegalArgumentException if either calendar is {@code null}
	 * @since 2.1
	 */
	public static boolean isSameDay(final Calendar cal1, final Calendar cal2) {
		if (cal1 == null || cal2 == null) {
			throw nullDateIllegalArgumentException();
		}
		return cal1.get(Calendar.ERA) == cal2.get(Calendar.ERA) && cal1.get(Calendar.YEAR) == cal2.get(Calendar.YEAR)
				&& cal1.get(Calendar.DAY_OF_YEAR) == cal2.get(Calendar.DAY_OF_YEAR);
	}

	// -----------------------------------------------------------------------
	/**
	 * <p>
	 * Checks if two date objects represent the same instant in time.
	 * </p>
	 *
	 * <p>
	 * This method compares the long millisecond time of the two objects.
	 * </p>
	 *
	 * @param date1 the first date, not altered, not null
	 * @param date2 the second date, not altered, not null
	 * @return true if they represent the same millisecond instant
	 * @throws IllegalArgumentException if either date is {@code null}
	 * @since 2.1
	 */
	public static boolean isSameInstant(final Date date1, final Date date2) {
		if (date1 == null || date2 == null) {
			throw nullDateIllegalArgumentException();
		}
		return date1.getTime() == date2.getTime();
	}

	/**
	 * <p>
	 * Checks if two calendar objects represent the same instant in time.
	 * </p>
	 *
	 * <p>
	 * This method compares the long millisecond time of the two objects.
	 * </p>
	 *
	 * @param cal1 the first calendar, not altered, not null
	 * @param cal2 the second calendar, not altered, not null
	 * @return true if they represent the same millisecond instant
	 * @throws IllegalArgumentException if either date is {@code null}
	 * @since 2.1
	 */
	public static boolean isSameInstant(final Calendar cal1, final Calendar cal2) {
		if (cal1 == null || cal2 == null) {
			throw nullDateIllegalArgumentException();
		}
		return cal1.getTime().getTime() == cal2.getTime().getTime();
	}

	// -----------------------------------------------------------------------
	/**
	 * <p>
	 * Checks if two calendar objects represent the same local time.
	 * </p>
	 *
	 * <p>
	 * This method compares the values of the fields of the two objects. In
	 * addition, both calendars must be the same of the same type.
	 * </p>
	 *
	 * @param cal1 the first calendar, not altered, not null
	 * @param cal2 the second calendar, not altered, not null
	 * @return true if they represent the same millisecond instant
	 * @throws IllegalArgumentException if either date is {@code null}
	 * @since 2.1
	 */
	public static boolean isSameLocalTime(final Calendar cal1, final Calendar cal2) {
		if (cal1 == null || cal2 == null) {
			throw nullDateIllegalArgumentException();
		}
		return cal1.get(Calendar.MILLISECOND) == cal2.get(Calendar.MILLISECOND)
				&& cal1.get(Calendar.SECOND) == cal2.get(Calendar.SECOND)
				&& cal1.get(Calendar.MINUTE) == cal2.get(Calendar.MINUTE)
				&& cal1.get(Calendar.HOUR_OF_DAY) == cal2.get(Calendar.HOUR_OF_DAY)
				&& cal1.get(Calendar.DAY_OF_YEAR) == cal2.get(Calendar.DAY_OF_YEAR)
				&& cal1.get(Calendar.YEAR) == cal2.get(Calendar.YEAR)
				&& cal1.get(Calendar.ERA) == cal2.get(Calendar.ERA) && cal1.getClass() == cal2.getClass();
	}

	// -----------------------------------------------------------------------
	/**
	 * <p>
	 * Parses a string representing a date by trying a variety of different parsers.
	 * </p>
	 *
	 * <p>
	 * The parse will try each parse pattern in turn. A parse is only deemed
	 * successful if it parses the whole of the input string. If no parse patterns
	 * match, a ParseException is thrown.
	 * </p>
	 * The parser will be lenient toward the parsed date.
	 *
	 * @param str           the date to parse, not null
	 * @param parsePatterns the date format patterns to use, see SimpleDateFormat,
	 *                      not null
	 * @return the parsed date
	 * @throws IllegalArgumentException if the date string or pattern array is null
	 * @throws ParseException           if none of the date patterns were suitable
	 *                                  (or there were none)
	 */
	public static Date parseDate(final String str, final String... parsePatterns) throws ParseException {
		return parseDate(str, null, parsePatterns);
	}

	// -----------------------------------------------------------------------
	/**
	 * <p>
	 * Parses a string representing a date by trying a variety of different parsers,
	 * using the default date format symbols for the given locale.
	 * </p>
	 *
	 * <p>
	 * The parse will try each parse pattern in turn. A parse is only deemed
	 * successful if it parses the whole of the input string. If no parse patterns
	 * match, a ParseException is thrown.
	 * </p>
	 * The parser will be lenient toward the parsed date.
	 *
	 * @param str           the date to parse, not null
	 * @param locale        the locale whose date format symbols should be used. If
	 *                      {@code null}, the system locale is used (as per
	 *                      {@link #parseDate(String, String...)}).
	 * @param parsePatterns the date format patterns to use, see SimpleDateFormat,
	 *                      not null
	 * @return the parsed date
	 * @throws IllegalArgumentException if the date string or pattern array is null
	 * @throws ParseException           if none of the date patterns were suitable
	 *                                  (or there were none)
	 * @since 3.2
	 */
	public static Date parseDate(final String str, final Locale locale, final String... parsePatterns)
			throws ParseException {
		return parseDateWithLeniency(str, locale, parsePatterns, true);
	}

	// -----------------------------------------------------------------------
	/**
	 * <p>
	 * Parses a string representing a date by trying a variety of different parsers.
	 * </p>
	 *
	 * <p>
	 * The parse will try each parse pattern in turn. A parse is only deemed
	 * successful if it parses the whole of the input string. If no parse patterns
	 * match, a ParseException is thrown.
	 * </p>
	 * The parser parses strictly - it does not allow for dates such as "February
	 * 942, 1996".
	 *
	 * @param str           the date to parse, not null
	 * @param parsePatterns the date format patterns to use, see SimpleDateFormat,
	 *                      not null
	 * @return the parsed date
	 * @throws IllegalArgumentException if the date string or pattern array is null
	 * @throws ParseException           if none of the date patterns were suitable
	 * @since 2.5
	 */
	public static Date parseDateStrictly(final String str, final String... parsePatterns) throws ParseException {
		return parseDateStrictly(str, null, parsePatterns);
	}

	/**
	 * <p>
	 * Parses a string representing a date by trying a variety of different parsers,
	 * using the default date format symbols for the given locale..
	 * </p>
	 *
	 * <p>
	 * The parse will try each parse pattern in turn. A parse is only deemed
	 * successful if it parses the whole of the input string. If no parse patterns
	 * match, a ParseException is thrown.
	 * </p>
	 * The parser parses strictly - it does not allow for dates such as "February
	 * 942, 1996".
	 *
	 * @param str           the date to parse, not null
	 * @param locale        the locale whose date format symbols should be used. If
	 *                      {@code null}, the system locale is used (as per
	 *                      {@link #parseDateStrictly(String, String...)}).
	 * @param parsePatterns the date format patterns to use, see SimpleDateFormat,
	 *                      not null
	 * @return the parsed date
	 * @throws IllegalArgumentException if the date string or pattern array is null
	 * @throws ParseException           if none of the date patterns were suitable
	 * @since 3.2
	 */
	public static Date parseDateStrictly(final String str, final Locale locale, final String... parsePatterns)
			throws ParseException {
		return parseDateWithLeniency(str, locale, parsePatterns, false);
	}

	/**
	 * <p>
	 * Parses a string representing a date by trying a variety of different parsers.
	 * </p>
	 *
	 * <p>
	 * The parse will try each parse pattern in turn. A parse is only deemed
	 * successful if it parses the whole of the input string. If no parse patterns
	 * match, a ParseException is thrown.
	 * </p>
	 *
	 * @param str           the date to parse, not null
	 * @param locale        the locale to use when interpreting the pattern, can be
	 *                      null in which case the default system locale is used
	 * @param parsePatterns the date format patterns to use, see SimpleDateFormat,
	 *                      not null
	 * @param lenient       Specify whether or not date/time parsing is to be
	 *                      lenient.
	 * @return the parsed date
	 * @throws IllegalArgumentException if the date string or pattern array is null
	 * @throws ParseException           if none of the date patterns were suitable
	 * @see java.util.Calendar#isLenient()
	 */
	private static Date parseDateWithLeniency(final String str, final Locale locale, final String[] parsePatterns,
			final boolean lenient) throws ParseException {
		if (str == null || parsePatterns == null) {
			throw new IllegalArgumentException("Date and Patterns must not be null");
		}

		final TimeZone tz = TimeZone.getDefault();
		final Locale lcl = LocaleUtils.toLocale(locale);
		final ParsePosition pos = new ParsePosition(0);
		final Calendar calendar = Calendar.getInstance(tz, lcl);
		calendar.setLenient(lenient);

		for (final String parsePattern : parsePatterns) {
			final FastDateParser fdp = new FastDateParser(parsePattern, tz, lcl);
			calendar.clear();
			try {
				if (fdp.parse(str, pos, calendar) && pos.getIndex() == str.length()) {
					return calendar.getTime();
				}
			} catch (final IllegalArgumentException ignore) {
				// leniency is preventing calendar from being set
			}
			pos.setIndex(0);
		}
		throw new ParseException("Unable to parse the date: " + str, -1);
	}

	// -----------------------------------------------------------------------
	/**
	 * Adds a number of years to a date returning a new object. The original
	 * {@code Date} is unchanged.
	 *
	 * @param date   the date, not null
	 * @param amount the amount to add, may be negative
	 * @return the new {@code Date} with the amount added
	 * @throws IllegalArgumentException if the date is null
	 */
	public static Date addYears(final Date date, final int amount) {
		return add(date, Calendar.YEAR, amount);
	}

	// -----------------------------------------------------------------------
	/**
	 * Adds a number of months to a date returning a new object. The original
	 * {@code Date} is unchanged.
	 *
	 * @param date   the date, not null
	 * @param amount the amount to add, may be negative
	 * @return the new {@code Date} with the amount added
	 * @throws IllegalArgumentException if the date is null
	 */
	public static Date addMonths(final Date date, final int amount) {
		return add(date, Calendar.MONTH, amount);
	}

	// -----------------------------------------------------------------------
	/**
	 * Adds a number of weeks to a date returning a new object. The original
	 * {@code Date} is unchanged.
	 *
	 * @param date   the date, not null
	 * @param amount the amount to add, may be negative
	 * @return the new {@code Date} with the amount added
	 * @throws IllegalArgumentException if the date is null
	 */
	public static Date addWeeks(final Date date, final int amount) {
		return add(date, Calendar.WEEK_OF_YEAR, amount);
	}

	// -----------------------------------------------------------------------
	/**
	 * Adds a number of days to a date returning a new object. The original
	 * {@code Date} is unchanged.
	 *
	 * @param date   the date, not null
	 * @param amount the amount to add, may be negative
	 * @return the new {@code Date} with the amount added
	 * @throws IllegalArgumentException if the date is null
	 */
	public static Date addDays(final Date date, final int amount) {
		return add(date, Calendar.DAY_OF_MONTH, amount);
	}

	// -----------------------------------------------------------------------
	/**
	 * Adds a number of hours to a date returning a new object. The original
	 * {@code Date} is unchanged.
	 *
	 * @param date   the date, not null
	 * @param amount the amount to add, may be negative
	 * @return the new {@code Date} with the amount added
	 * @throws IllegalArgumentException if the date is null
	 */
	public static Date addHours(final Date date, final int amount) {
		return add(date, Calendar.HOUR_OF_DAY, amount);
	}

	// -----------------------------------------------------------------------
	/**
	 * Adds a number of minutes to a date returning a new object. The original
	 * {@code Date} is unchanged.
	 *
	 * @param date   the date, not null
	 * @param amount the amount to add, may be negative
	 * @return the new {@code Date} with the amount added
	 * @throws IllegalArgumentException if the date is null
	 */
	public static Date addMinutes(final Date date, final int amount) {
		return add(date, Calendar.MINUTE, amount);
	}

	// -----------------------------------------------------------------------
	/**
	 * Adds a number of seconds to a date returning a new object. The original
	 * {@code Date} is unchanged.
	 *
	 * @param date   the date, not null
	 * @param amount the amount to add, may be negative
	 * @return the new {@code Date} with the amount added
	 * @throws IllegalArgumentException if the date is null
	 */
	public static Date addSeconds(final Date date, final int amount) {
		return add(date, Calendar.SECOND, amount);
	}

	// -----------------------------------------------------------------------
	/**
	 * Adds a number of milliseconds to a date returning a new object. The original
	 * {@code Date} is unchanged.
	 *
	 * @param date   the date, not null
	 * @param amount the amount to add, may be negative
	 * @return the new {@code Date} with the amount added
	 * @throws IllegalArgumentException if the date is null
	 */
	public static Date addMilliseconds(final Date date, final int amount) {
		return add(date, Calendar.MILLISECOND, amount);
	}

	// -----------------------------------------------------------------------
	/**
	 * Adds to a date returning a new object. The original {@code Date} is
	 * unchanged.
	 *
	 * @param date          the date, not null
	 * @param calendarField the calendar field to add to
	 * @param amount        the amount to add, may be negative
	 * @return the new {@code Date} with the amount added
	 * @throws NullPointerException if the date is null
	 */
	private static Date add(final Date date, final int calendarField, final int amount) {
		validateDateNotNull(date);
		final Calendar c = Calendar.getInstance();
		c.setTime(date);
		c.add(calendarField, amount);
		return c.getTime();
	}

	// -----------------------------------------------------------------------
	/**
	 * Sets the years field to a date returning a new object. The original
	 * {@code Date} is unchanged.
	 *
	 * @param date   the date, not null
	 * @param amount the amount to set
	 * @return a new {@code Date} set with the specified value
	 * @throws IllegalArgumentException if the date is null
	 * @since 2.4
	 */
	public static Date setYears(final Date date, final int amount) {
		return set(date, Calendar.YEAR, amount);
	}

	// -----------------------------------------------------------------------
	/**
	 * Sets the months field to a date returning a new object. The original
	 * {@code Date} is unchanged.
	 *
	 * @param date   the date, not null
	 * @param amount the amount to set
	 * @return a new {@code Date} set with the specified value
	 * @throws IllegalArgumentException if the date is null
	 * @since 2.4
	 */
	public static Date setMonths(final Date date, final int amount) {
		return set(date, Calendar.MONTH, amount);
	}

	// -----------------------------------------------------------------------
	/**
	 * Sets the day of month field to a date returning a new object. The original
	 * {@code Date} is unchanged.
	 *
	 * @param date   the date, not null
	 * @param amount the amount to set
	 * @return a new {@code Date} set with the specified value
	 * @throws IllegalArgumentException if the date is null
	 * @since 2.4
	 */
	public static Date setDays(final Date date, final int amount) {
		return set(date, Calendar.DAY_OF_MONTH, amount);
	}

	// -----------------------------------------------------------------------
	/**
	 * Sets the hours field to a date returning a new object. Hours range from 0-23.
	 * The original {@code Date} is unchanged.
	 *
	 * @param date   the date, not null
	 * @param amount the amount to set
	 * @return a new {@code Date} set with the specified value
	 * @throws IllegalArgumentException if the date is null
	 * @since 2.4
	 */
	public static Date setHours(final Date date, final int amount) {
		return set(date, Calendar.HOUR_OF_DAY, amount);
	}

	// -----------------------------------------------------------------------
	/**
	 * Sets the minute field to a date returning a new object. The original
	 * {@code Date} is unchanged.
	 *
	 * @param date   the date, not null
	 * @param amount the amount to set
	 * @return a new {@code Date} set with the specified value
	 * @throws IllegalArgumentException if the date is null
	 * @since 2.4
	 */
	public static Date setMinutes(final Date date, final int amount) {
		return set(date, Calendar.MINUTE, amount);
	}

	// -----------------------------------------------------------------------
	/**
	 * Sets the seconds field to a date returning a new object. The original
	 * {@code Date} is unchanged.
	 *
	 * @param date   the date, not null
	 * @param amount the amount to set
	 * @return a new {@code Date} set with the specified value
	 * @throws IllegalArgumentException if the date is null
	 * @since 2.4
	 */
	public static Date setSeconds(final Date date, final int amount) {
		return set(date, Calendar.SECOND, amount);
	}

	// -----------------------------------------------------------------------
	/**
	 * Sets the milliseconds field to a date returning a new object. The original
	 * {@code Date} is unchanged.
	 *
	 * @param date   the date, not null
	 * @param amount the amount to set
	 * @return a new {@code Date} set with the specified value
	 * @throws IllegalArgumentException if the date is null
	 * @since 2.4
	 */
	public static Date setMilliseconds(final Date date, final int amount) {
		return set(date, Calendar.MILLISECOND, amount);
	}

	// -----------------------------------------------------------------------
	/**
	 * Sets the specified field to a date returning a new object. This does not use
	 * a lenient calendar. The original {@code Date} is unchanged.
	 *
	 * @param date          the date, not null
	 * @param calendarField the {@code Calendar} field to set the amount to
	 * @param amount        the amount to set
	 * @return a new {@code Date} set with the specified value
	 * @throws IllegalArgumentException if the date is null
	 * @since 2.4
	 */
	private static Date set(final Date date, final int calendarField, final int amount) {
		validateDateNotNull(date);
		// getInstance() returns a new object, so this method is thread safe.
		final Calendar c = Calendar.getInstance();
		c.setLenient(false);
		c.setTime(date);
		c.set(calendarField, amount);
		return c.getTime();
	}

	// -----------------------------------------------------------------------
	/**
	 * Converts a {@code Date} into a {@code Calendar}.
	 *
	 * @param date the date to convert to a Calendar
	 * @return the created Calendar
	 * @throws NullPointerException if null is passed in
	 * @since 3.0
	 */
	public static Calendar toCalendar(final Date date) {
		final Calendar c = Calendar.getInstance();
		c.setTime(date);
		return c;
	}

	// -----------------------------------------------------------------------
	/**
	 * Converts a {@code Date} of a given {@code TimeZone} into a {@code Calendar}
	 * 
	 * @param date the date to convert to a Calendar
	 * @param tz   the time zone of the {@code date}
	 * @return the created Calendar
	 * @throws NullPointerException if {@code date} or {@code tz} is null
	 */
	public static Calendar toCalendar(final Date date, final TimeZone tz) {
		final Calendar c = Calendar.getInstance(tz);
		c.setTime(date);
		return c;
	}

	// -----------------------------------------------------------------------
	/**
	 * <p>
	 * Rounds a date, leaving the field specified as the most significant field.
	 * </p>
	 *
	 * <p>
	 * For example, if you had the date-time of 28 Mar 2002 13:45:01.231, if this
	 * was passed with HOUR, it would return 28 Mar 2002 14:00:00.000. If this was
	 * passed with MONTH, it would return 1 April 2002 0:00:00.000.
	 * </p>
	 *
	 * <p>
	 * For a date in a time zone that handles the change to daylight saving time,
	 * rounding to Calendar.HOUR_OF_DAY will behave as follows. Suppose daylight
	 * saving time begins at 02:00 on March 30. Rounding a date that crosses this
	 * time would produce the following values:
	 * </p>
	 * <ul>
	 * <li>March 30, 2003 01:10 rounds to March 30, 2003 01:00</li>
	 * <li>March 30, 2003 01:40 rounds to March 30, 2003 03:00</li>
	 * <li>March 30, 2003 02:10 rounds to March 30, 2003 03:00</li>
	 * <li>March 30, 2003 02:40 rounds to March 30, 2003 04:00</li>
	 * </ul>
	 *
	 * @param date  the date to work with, not null
	 * @param field the field from {@code Calendar} or {@code SEMI_MONTH}
	 * @return the different rounded date, not null
	 * @throws ArithmeticException if the year is over 280 million
	 */
	public static Date round(final Date date, final int field) {
		validateDateNotNull(date);
		final Calendar gval = Calendar.getInstance();
		gval.setTime(date);
		modify(gval, field, ModifyType.ROUND);
		return gval.getTime();
	}

	/**
	 * <p>
	 * Rounds a date, leaving the field specified as the most significant field.
	 * </p>
	 *
	 * <p>
	 * For example, if you had the date-time of 28 Mar 2002 13:45:01.231, if this
	 * was passed with HOUR, it would return 28 Mar 2002 14:00:00.000. If this was
	 * passed with MONTH, it would return 1 April 2002 0:00:00.000.
	 * </p>
	 *
	 * <p>
	 * For a date in a time zone that handles the change to daylight saving time,
	 * rounding to Calendar.HOUR_OF_DAY will behave as follows. Suppose daylight
	 * saving time begins at 02:00 on March 30. Rounding a date that crosses this
	 * time would produce the following values:
	 * </p>
	 * <ul>
	 * <li>March 30, 2003 01:10 rounds to March 30, 2003 01:00</li>
	 * <li>March 30, 2003 01:40 rounds to March 30, 2003 03:00</li>
	 * <li>March 30, 2003 02:10 rounds to March 30, 2003 03:00</li>
	 * <li>March 30, 2003 02:40 rounds to March 30, 2003 04:00</li>
	 * </ul>
	 *
	 * @param date  the date to work with, not null
	 * @param field the field from {@code Calendar} or {@code SEMI_MONTH}
	 * @return the different rounded date, not null
	 * @throws NullPointerException if the date is {@code null}
	 * @throws ArithmeticException  if the year is over 280 million
	 */
	public static Calendar round(final Calendar date, final int field) {
		if (date == null) {
			throw nullDateIllegalArgumentException();
		}
		final Calendar rounded = (Calendar) date.clone();
		modify(rounded, field, ModifyType.ROUND);
		return rounded;
	}

	private static IllegalArgumentException nullDateIllegalArgumentException() {
		return new IllegalArgumentException("The date must not be null");
	}

	/**
	 * <p>
	 * Rounds a date, leaving the field specified as the most significant field.
	 * </p>
	 *
	 * <p>
	 * For example, if you had the date-time of 28 Mar 2002 13:45:01.231, if this
	 * was passed with HOUR, it would return 28 Mar 2002 14:00:00.000. If this was
	 * passed with MONTH, it would return 1 April 2002 0:00:00.000.
	 * </p>
	 *
	 * <p>
	 * For a date in a time zone that handles the change to daylight saving time,
	 * rounding to Calendar.HOUR_OF_DAY will behave as follows. Suppose daylight
	 * saving time begins at 02:00 on March 30. Rounding a date that crosses this
	 * time would produce the following values:
	 * </p>
	 * <ul>
	 * <li>March 30, 2003 01:10 rounds to March 30, 2003 01:00</li>
	 * <li>March 30, 2003 01:40 rounds to March 30, 2003 03:00</li>
	 * <li>March 30, 2003 02:10 rounds to March 30, 2003 03:00</li>
	 * <li>March 30, 2003 02:40 rounds to March 30, 2003 04:00</li>
	 * </ul>
	 *
	 * @param date  the date to work with, either {@code Date} or {@code Calendar},
	 *              not null
	 * @param field the field from {@code Calendar} or {@code SEMI_MONTH}
	 * @return the different rounded date, not null
	 * @throws NullPointerException if the date is {@code null}
	 * @throws ClassCastException   if the object type is not a {@code Date} or
	 *                              {@code Calendar}
	 * @throws ArithmeticException  if the year is over 280 million
	 */
	public static Date round(final Object date, final int field) {
		if (date == null) {
			throw nullDateIllegalArgumentException();
		}
		if (date instanceof Date) {
			return round((Date) date, field);
		} else if (date instanceof Calendar) {
			return round((Calendar) date, field).getTime();
		} else {
			throw new ClassCastException("Could not round " + date);
		}
	}

	// -----------------------------------------------------------------------
	/**
	 * <p>
	 * Truncates a date, leaving the field specified as the most significant field.
	 * </p>
	 *
	 * <p>
	 * For example, if you had the date-time of 28 Mar 2002 13:45:01.231, if you
	 * passed with HOUR, it would return 28 Mar 2002 13:00:00.000. If this was
	 * passed with MONTH, it would return 1 Mar 2002 0:00:00.000.
	 * </p>
	 *
	 * @param date  the date to work with, not null
	 * @param field the field from {@code Calendar} or {@code SEMI_MONTH}
	 * @return the different truncated date, not null
	 * @throws NullPointerException if the date is {@code null}
	 * @throws ArithmeticException  if the year is over 280 million
	 */
	public static Date truncate(final Date date, final int field) {
		validateDateNotNull(date);
		final Calendar gval = Calendar.getInstance();
		gval.setTime(date);
		modify(gval, field, ModifyType.TRUNCATE);
		return gval.getTime();
	}

	/**
	 * <p>
	 * Truncates a date, leaving the field specified as the most significant field.
	 * </p>
	 *
	 * <p>
	 * For example, if you had the date-time of 28 Mar 2002 13:45:01.231, if you
	 * passed with HOUR, it would return 28 Mar 2002 13:00:00.000. If this was
	 * passed with MONTH, it would return 1 Mar 2002 0:00:00.000.
	 * </p>
	 *
	 * @param date  the date to work with, not null
	 * @param field the field from {@code Calendar} or {@code SEMI_MONTH}
	 * @return the different truncated date, not null
	 * @throws NullPointerException if the date is {@code null}
	 * @throws ArithmeticException  if the year is over 280 million
	 */
	public static Calendar truncate(final Calendar date, final int field) {
		if (date == null) {
			throw nullDateIllegalArgumentException();
		}
		final Calendar truncated = (Calendar) date.clone();
		modify(truncated, field, ModifyType.TRUNCATE);
		return truncated;
	}

	/**
	 * <p>
	 * Truncates a date, leaving the field specified as the most significant field.
	 * </p>
	 *
	 * <p>
	 * For example, if you had the date-time of 28 Mar 2002 13:45:01.231, if you
	 * passed with HOUR, it would return 28 Mar 2002 13:00:00.000. If this was
	 * passed with MONTH, it would return 1 Mar 2002 0:00:00.000.
	 * </p>
	 *
	 * @param date  the date to work with, either {@code Date} or {@code Calendar},
	 *              not null
	 * @param field the field from {@code Calendar} or {@code SEMI_MONTH}
	 * @return the different truncated date, not null
	 * @throws NullPointerException if the date is {@code null}
	 * @throws ClassCastException   if the object type is not a {@code Date} or
	 *                              {@code Calendar}
	 * @throws ArithmeticException  if the year is over 280 million
	 */
	public static Date truncate(final Object date, final int field) {
		if (date == null) {
			throw nullDateIllegalArgumentException();
		}
		if (date instanceof Date) {
			return truncate((Date) date, field);
		} else if (date instanceof Calendar) {
			return truncate((Calendar) date, field).getTime();
		} else {
			throw new ClassCastException("Could not truncate " + date);
		}
	}

	// -----------------------------------------------------------------------
	/**
	 * <p>
	 * Gets a date ceiling, leaving the field specified as the most significant
	 * field.
	 * </p>
	 *
	 * <p>
	 * For example, if you had the date-time of 28 Mar 2002 13:45:01.231, if you
	 * passed with HOUR, it would return 28 Mar 2002 14:00:00.000. If this was
	 * passed with MONTH, it would return 1 Apr 2002 0:00:00.000.
	 * </p>
	 *
	 * @param date  the date to work with, not null
	 * @param field the field from {@code Calendar} or {@code SEMI_MONTH}
	 * @return the different ceil date, not null
	 * @throws NullPointerException if the date is {@code null}
	 * @throws ArithmeticException  if the year is over 280 million
	 * @since 2.5
	 */
	public static Date ceiling(final Date date, final int field) {
		validateDateNotNull(date);
		final Calendar gval = Calendar.getInstance();
		gval.setTime(date);
		modify(gval, field, ModifyType.CEILING);
		return gval.getTime();
	}

	/**
	 * <p>
	 * Gets a date ceiling, leaving the field specified as the most significant
	 * field.
	 * </p>
	 *
	 * <p>
	 * For example, if you had the date-time of 28 Mar 2002 13:45:01.231, if you
	 * passed with HOUR, it would return 28 Mar 2002 14:00:00.000. If this was
	 * passed with MONTH, it would return 1 Apr 2002 0:00:00.000.
	 * </p>
	 *
	 * @param date  the date to work with, not null
	 * @param field the field from {@code Calendar} or {@code SEMI_MONTH}
	 * @return the different ceil date, not null
	 * @throws NullPointerException if the date is {@code null}
	 * @throws ArithmeticException  if the year is over 280 million
	 * @since 2.5
	 */
	public static Calendar ceiling(final Calendar date, final int field) {
		if (date == null) {
			throw nullDateIllegalArgumentException();
		}
		final Calendar ceiled = (Calendar) date.clone();
		modify(ceiled, field, ModifyType.CEILING);
		return ceiled;
	}

	/**
	 * <p>
	 * Gets a date ceiling, leaving the field specified as the most significant
	 * field.
	 * </p>
	 *
	 * <p>
	 * For example, if you had the date-time of 28 Mar 2002 13:45:01.231, if you
	 * passed with HOUR, it would return 28 Mar 2002 14:00:00.000. If this was
	 * passed with MONTH, it would return 1 Apr 2002 0:00:00.000.
	 * </p>
	 *
	 * @param date  the date to work with, either {@code Date} or {@code Calendar},
	 *              not null
	 * @param field the field from {@code Calendar} or {@code SEMI_MONTH}
	 * @return the different ceil date, not null
	 * @throws NullPointerException if the date is {@code null}
	 * @throws ClassCastException   if the object type is not a {@code Date} or
	 *                              {@code Calendar}
	 * @throws ArithmeticException  if the year is over 280 million
	 * @since 2.5
	 */
	public static Date ceiling(final Object date, final int field) {
		if (date == null) {
			throw nullDateIllegalArgumentException();
		}
		if (date instanceof Date) {
			return ceiling((Date) date, field);
		} else if (date instanceof Calendar) {
			return ceiling((Calendar) date, field).getTime();
		} else {
			throw new ClassCastException("Could not find ceiling of for type: " + date.getClass());
		}
	}

	// -----------------------------------------------------------------------
	/**
	 * <p>
	 * Internal calculation method.
	 * </p>
	 *
	 * @param val     the calendar, not null
	 * @param field   the field constant
	 * @param modType type to truncate, round or ceiling
	 * @throws ArithmeticException if the year is over 280 million
	 */
	private static void modify(final Calendar val, final int field, final ModifyType modType) {
		if (val.get(Calendar.YEAR) > 280000000) {
			throw new ArithmeticException("Calendar value too large for accurate calculations");
		}

		if (field == Calendar.MILLISECOND) {
			return;
		}

		// ----------------- Fix for LANG-59 ---------------------- START
		// ---------------
		// see https://issues.apache.org/jira/browse/LANG-59
		//
		// Manually truncate milliseconds, seconds and minutes, rather than using
		// Calendar methods.

		final Date date = val.getTime();
		long time = date.getTime();
		boolean done = false;

		// truncate milliseconds
		final int millisecs = val.get(Calendar.MILLISECOND);
		if (ModifyType.TRUNCATE == modType || millisecs < 500) {
			time = time - millisecs;
		}
		if (field == Calendar.SECOND) {
			done = true;
		}

		// truncate seconds
		final int seconds = val.get(Calendar.SECOND);
		if (!done && (ModifyType.TRUNCATE == modType || seconds < 30)) {
			time = time - (seconds * 1000L);
		}
		if (field == Calendar.MINUTE) {
			done = true;
		}

		// truncate minutes
		final int minutes = val.get(Calendar.MINUTE);
		if (!done && (ModifyType.TRUNCATE == modType || minutes < 30)) {
			time = time - (minutes * 60000L);
		}

		// reset time
		if (date.getTime() != time) {
			date.setTime(time);
			val.setTime(date);
		}
		// ----------------- Fix for LANG-59 ----------------------- END
		// ----------------

		boolean roundUp = false;
		for (final int[] aField : fields) {
			for (final int element : aField) {
				if (element == field) {
					// This is our field... we stop looping
					if (modType == ModifyType.CEILING || modType == ModifyType.ROUND && roundUp) {
						if (field == SEMI_MONTH) {
							// This is a special case that's hard to generalize
							// If the date is 1, we round up to 16, otherwise
							// we subtract 15 days and add 1 month
							if (val.get(Calendar.DATE) == 1) {
								val.add(Calendar.DATE, 15);
							} else {
								val.add(Calendar.DATE, -15);
								val.add(Calendar.MONTH, 1);
							}
// ----------------- Fix for LANG-440 ---------------------- START ---------------
						} else if (field == Calendar.AM_PM) {
							// This is a special case
							// If the time is 0, we round up to 12, otherwise
							// we subtract 12 hours and add 1 day
							if (val.get(Calendar.HOUR_OF_DAY) == 0) {
								val.add(Calendar.HOUR_OF_DAY, 12);
							} else {
								val.add(Calendar.HOUR_OF_DAY, -12);
								val.add(Calendar.DATE, 1);
							}
// ----------------- Fix for LANG-440 ---------------------- END ---------------
						} else {
							// We need at add one to this field since the
							// last number causes us to round up
							val.add(aField[0], 1);
						}
					}
					return;
				}
			}
			// We have various fields that are not easy roundings
			int offset = 0;
			boolean offsetSet = false;
			// These are special types of fields that require different rounding rules
			switch (field) {
			case SEMI_MONTH:
				if (aField[0] == Calendar.DATE) {
					// If we're going to drop the DATE field's value,
					// we want to do this our own way.
					// We need to subtract 1 since the date has a minimum of 1
					offset = val.get(Calendar.DATE) - 1;
					// If we're above 15 days adjustment, that means we're in the
					// bottom half of the month and should stay accordingly.
					if (offset >= 15) {
						offset -= 15;
					}
					// Record whether we're in the top or bottom half of that range
					roundUp = offset > 7;
					offsetSet = true;
				}
				break;
			case Calendar.AM_PM:
				if (aField[0] == Calendar.HOUR_OF_DAY) {
					// If we're going to drop the HOUR field's value,
					// we want to do this our own way.
					offset = val.get(Calendar.HOUR_OF_DAY);
					if (offset >= 12) {
						offset -= 12;
					}
					roundUp = offset >= 6;
					offsetSet = true;
				}
				break;
			default:
				break;
			}
			if (!offsetSet) {
				final int min = val.getActualMinimum(aField[0]);
				final int max = val.getActualMaximum(aField[0]);
				// Calculate the offset from the minimum allowed value
				offset = val.get(aField[0]) - min;
				// Set roundUp if this is more than half way between the minimum and maximum
				roundUp = offset > ((max - min) / 2);
			}
			// We need to remove this field
			if (offset != 0) {
				val.set(aField[0], val.get(aField[0]) - offset);
			}
		}
		throw new IllegalArgumentException("The field " + field + " is not supported");

	}

	// -----------------------------------------------------------------------
	/**
	 * <p>
	 * Constructs an {@code Iterator} over each day in a date range defined by a
	 * focus date and range style.
	 * </p>
	 *
	 * <p>
	 * For instance, passing Thursday, July 4, 2002 and a {@code RANGE_MONTH_SUNDAY}
	 * will return an {@code Iterator} that starts with Sunday, June 30, 2002 and
	 * ends with Saturday, August 3, 2002, returning a Calendar instance for each
	 * intermediate day.
	 * </p>
	 *
	 * <p>
	 * This method provides an iterator that returns Calendar objects. The days are
	 * progressed using {@link Calendar#add(int, int)}.
	 * </p>
	 *
	 * @param focus      the date to work with, not null
	 * @param rangeStyle the style constant to use. Must be one of
	 *                   {@link DateUtils#RANGE_MONTH_SUNDAY},
	 *                   {@link DateUtils#RANGE_MONTH_MONDAY},
	 *                   {@link DateUtils#RANGE_WEEK_SUNDAY},
	 *                   {@link DateUtils#RANGE_WEEK_MONDAY},
	 *                   {@link DateUtils#RANGE_WEEK_RELATIVE},
	 *                   {@link DateUtils#RANGE_WEEK_CENTER}
	 * @return the date iterator, not null, not null
	 * @throws NullPointerException     if the date is {@code null}
	 * @throws IllegalArgumentException if the rangeStyle is invalid
	 */
	public static Iterator<Calendar> iterator(final Date focus, final int rangeStyle) {
		validateDateNotNull(focus);
		final Calendar gval = Calendar.getInstance();
		gval.setTime(focus);
		return iterator(gval, rangeStyle);
	}

	/**
	 * <p>
	 * Constructs an {@code Iterator} over each day in a date range defined by a
	 * focus date and range style.
	 * </p>
	 *
	 * <p>
	 * For instance, passing Thursday, July 4, 2002 and a {@code RANGE_MONTH_SUNDAY}
	 * will return an {@code Iterator} that starts with Sunday, June 30, 2002 and
	 * ends with Saturday, August 3, 2002, returning a Calendar instance for each
	 * intermediate day.
	 * </p>
	 *
	 * <p>
	 * This method provides an iterator that returns Calendar objects. The days are
	 * progressed using {@link Calendar#add(int, int)}.
	 * </p>
	 *
	 * @param focus      the date to work with, not null
	 * @param rangeStyle the style constant to use. Must be one of
	 *                   {@link DateUtils#RANGE_MONTH_SUNDAY},
	 *                   {@link DateUtils#RANGE_MONTH_MONDAY},
	 *                   {@link DateUtils#RANGE_WEEK_SUNDAY},
	 *                   {@link DateUtils#RANGE_WEEK_MONDAY},
	 *                   {@link DateUtils#RANGE_WEEK_RELATIVE},
	 *                   {@link DateUtils#RANGE_WEEK_CENTER}
	 * @return the date iterator, not null
	 * @throws IllegalArgumentException if the date is {@code null}
	 * @throws IllegalArgumentException if the rangeStyle is invalid
	 */
	public static Iterator<Calendar> iterator(final Calendar focus, final int rangeStyle) {
		if (focus == null) {
			throw nullDateIllegalArgumentException();
		}
		Calendar start = null;
		Calendar end = null;
		int startCutoff = Calendar.SUNDAY;
		int endCutoff = Calendar.SATURDAY;
		switch (rangeStyle) {
		case RANGE_MONTH_SUNDAY:
		case RANGE_MONTH_MONDAY:
			// Set start to the first of the month
			start = truncate(focus, Calendar.MONTH);
			// Set end to the last of the month
			end = (Calendar) start.clone();
			end.add(Calendar.MONTH, 1);
			end.add(Calendar.DATE, -1);
			// Loop start back to the previous sunday or monday
			if (rangeStyle == RANGE_MONTH_MONDAY) {
				startCutoff = Calendar.MONDAY;
				endCutoff = Calendar.SUNDAY;
			}
			break;
		case RANGE_WEEK_SUNDAY:
		case RANGE_WEEK_MONDAY:
		case RANGE_WEEK_RELATIVE:
		case RANGE_WEEK_CENTER:
			// Set start and end to the current date
			start = truncate(focus, Calendar.DATE);
			end = truncate(focus, Calendar.DATE);
			switch (rangeStyle) {
			case RANGE_WEEK_SUNDAY:
				// already set by default
				break;
			case RANGE_WEEK_MONDAY:
				startCutoff = Calendar.MONDAY;
				endCutoff = Calendar.SUNDAY;
				break;
			case RANGE_WEEK_RELATIVE:
				startCutoff = focus.get(Calendar.DAY_OF_WEEK);
				endCutoff = startCutoff - 1;
				break;
			case RANGE_WEEK_CENTER:
				startCutoff = focus.get(Calendar.DAY_OF_WEEK) - 3;
				endCutoff = focus.get(Calendar.DAY_OF_WEEK) + 3;
				break;
			default:
				break;
			}
			break;
		default:
			throw new IllegalArgumentException("The range style " + rangeStyle + " is not valid.");
		}
		if (startCutoff < Calendar.SUNDAY) {
			startCutoff += 7;
		}
		if (startCutoff > Calendar.SATURDAY) {
			startCutoff -= 7;
		}
		if (endCutoff < Calendar.SUNDAY) {
			endCutoff += 7;
		}
		if (endCutoff > Calendar.SATURDAY) {
			endCutoff -= 7;
		}
		while (start.get(Calendar.DAY_OF_WEEK) != startCutoff) {
			start.add(Calendar.DATE, -1);
		}
		while (end.get(Calendar.DAY_OF_WEEK) != endCutoff) {
			end.add(Calendar.DATE, 1);
		}
		return new DateIterator(start, end);
	}

	/**
	 * <p>
	 * Constructs an {@code Iterator} over each day in a date range defined by a
	 * focus date and range style.
	 * </p>
	 *
	 * <p>
	 * For instance, passing Thursday, July 4, 2002 and a {@code RANGE_MONTH_SUNDAY}
	 * will return an {@code Iterator} that starts with Sunday, June 30, 2002 and
	 * ends with Saturday, August 3, 2002, returning a Calendar instance for each
	 * intermediate day.
	 * </p>
	 *
	 * @param focus      the date to work with, either {@code Date} or
	 *                   {@code Calendar}, not null
	 * @param rangeStyle the style constant to use. Must be one of the range styles
	 *                   listed for the {@link #iterator(Calendar, int)} method.
	 * @return the date iterator, not null
	 * @throws IllegalArgumentException if the date is {@code null}
	 * @throws ClassCastException       if the object type is not a {@code Date} or
	 *                                  {@code Calendar}
	 */
	public static Iterator<?> iterator(final Object focus, final int rangeStyle) {
		if (focus == null) {
			throw nullDateIllegalArgumentException();
		}
		if (focus instanceof Date) {
			return iterator((Date) focus, rangeStyle);
		} else if (focus instanceof Calendar) {
			return iterator((Calendar) focus, rangeStyle);
		} else {
			throw new ClassCastException("Could not iterate based on " + focus);
		}
	}

	/**
	 * <p>
	 * Returns the number of milliseconds within the fragment. All datefields
	 * greater than the fragment will be ignored.
	 * </p>
	 *
	 * <p>
	 * Asking the milliseconds of any date will only return the number of
	 * milliseconds of the current second (resulting in a number between 0 and 999).
	 * This method will retrieve the number of milliseconds for any fragment. For
	 * example, if you want to calculate the number of milliseconds past today, your
	 * fragment is Calendar.DATE or Calendar.DAY_OF_YEAR. The result will be all
	 * milliseconds of the past hour(s), minutes(s) and second(s).
	 * </p>
	 *
	 * <p>
	 * Valid fragments are: Calendar.YEAR, Calendar.MONTH, both Calendar.DAY_OF_YEAR
	 * and Calendar.DATE, Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND and
	 * Calendar.MILLISECOND A fragment less than or equal to a SECOND field will
	 * return 0.
	 * </p>
	 *
	 * <ul>
	 * <li>January 1, 2008 7:15:10.538 with Calendar.SECOND as fragment will return
	 * 538</li>
	 * <li>January 6, 2008 7:15:10.538 with Calendar.SECOND as fragment will return
	 * 538</li>
	 * <li>January 6, 2008 7:15:10.538 with Calendar.MINUTE as fragment will return
	 * 10538 (10*1000 + 538)</li>
	 * <li>January 16, 2008 7:15:10.538 with Calendar.MILLISECOND as fragment will
	 * return 0 (a millisecond cannot be split in milliseconds)</li>
	 * </ul>
	 *
	 * @param date     the date to work with, not null
	 * @param fragment the {@code Calendar} field part of date to calculate
	 * @return number of milliseconds within the fragment of date
	 * @throws IllegalArgumentException if the date is {@code null} or fragment is
	 *                                  not supported
	 * @since 2.4
	 */
	public static long getFragmentInMilliseconds(final Date date, final int fragment) {
		return getFragment(date, fragment, TimeUnit.MILLISECONDS);
	}

	/**
	 * <p>
	 * Returns the number of seconds within the fragment. All datefields greater
	 * than the fragment will be ignored.
	 * </p>
	 *
	 * <p>
	 * Asking the seconds of any date will only return the number of seconds of the
	 * current minute (resulting in a number between 0 and 59). This method will
	 * retrieve the number of seconds for any fragment. For example, if you want to
	 * calculate the number of seconds past today, your fragment is Calendar.DATE or
	 * Calendar.DAY_OF_YEAR. The result will be all seconds of the past hour(s) and
	 * minutes(s).
	 * </p>
	 *
	 * <p>
	 * Valid fragments are: Calendar.YEAR, Calendar.MONTH, both Calendar.DAY_OF_YEAR
	 * and Calendar.DATE, Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND and
	 * Calendar.MILLISECOND A fragment less than or equal to a SECOND field will
	 * return 0.
	 * </p>
	 *
	 * <ul>
	 * <li>January 1, 2008 7:15:10.538 with Calendar.MINUTE as fragment will return
	 * 10 (equivalent to deprecated date.getSeconds())</li>
	 * <li>January 6, 2008 7:15:10.538 with Calendar.MINUTE as fragment will return
	 * 10 (equivalent to deprecated date.getSeconds())</li>
	 * <li>January 6, 2008 7:15:10.538 with Calendar.DAY_OF_YEAR as fragment will
	 * return 26110 (7*3600 + 15*60 + 10)</li>
	 * <li>January 16, 2008 7:15:10.538 with Calendar.MILLISECOND as fragment will
	 * return 0 (a millisecond cannot be split in seconds)</li>
	 * </ul>
	 *
	 * @param date     the date to work with, not null
	 * @param fragment the {@code Calendar} field part of date to calculate
	 * @return number of seconds within the fragment of date
	 * @throws IllegalArgumentException if the date is {@code null} or fragment is
	 *                                  not supported
	 * @since 2.4
	 */
	public static long getFragmentInSeconds(final Date date, final int fragment) {
		return getFragment(date, fragment, TimeUnit.SECONDS);
	}

	/**
	 * <p>
	 * Returns the number of minutes within the fragment. All datefields greater
	 * than the fragment will be ignored.
	 * </p>
	 *
	 * <p>
	 * Asking the minutes of any date will only return the number of minutes of the
	 * current hour (resulting in a number between 0 and 59). This method will
	 * retrieve the number of minutes for any fragment. For example, if you want to
	 * calculate the number of minutes past this month, your fragment is
	 * Calendar.MONTH. The result will be all minutes of the past day(s) and
	 * hour(s).
	 * </p>
	 *
	 * <p>
	 * Valid fragments are: Calendar.YEAR, Calendar.MONTH, both Calendar.DAY_OF_YEAR
	 * and Calendar.DATE, Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND and
	 * Calendar.MILLISECOND A fragment less than or equal to a MINUTE field will
	 * return 0.
	 * </p>
	 *
	 * <ul>
	 * <li>January 1, 2008 7:15:10.538 with Calendar.HOUR_OF_DAY as fragment will
	 * return 15 (equivalent to deprecated date.getMinutes())</li>
	 * <li>January 6, 2008 7:15:10.538 with Calendar.HOUR_OF_DAY as fragment will
	 * return 15 (equivalent to deprecated date.getMinutes())</li>
	 * <li>January 1, 2008 7:15:10.538 with Calendar.MONTH as fragment will return
	 * 15</li>
	 * <li>January 6, 2008 7:15:10.538 with Calendar.MONTH as fragment will return
	 * 435 (7*60 + 15)</li>
	 * <li>January 16, 2008 7:15:10.538 with Calendar.MILLISECOND as fragment will
	 * return 0 (a millisecond cannot be split in minutes)</li>
	 * </ul>
	 *
	 * @param date     the date to work with, not null
	 * @param fragment the {@code Calendar} field part of date to calculate
	 * @return number of minutes within the fragment of date
	 * @throws IllegalArgumentException if the date is {@code null} or fragment is
	 *                                  not supported
	 * @since 2.4
	 */
	public static long getFragmentInMinutes(final Date date, final int fragment) {
		return getFragment(date, fragment, TimeUnit.MINUTES);
	}

	/**
	 * <p>
	 * Returns the number of hours within the fragment. All datefields greater than
	 * the fragment will be ignored.
	 * </p>
	 *
	 * <p>
	 * Asking the hours of any date will only return the number of hours of the
	 * current day (resulting in a number between 0 and 23). This method will
	 * retrieve the number of hours for any fragment. For example, if you want to
	 * calculate the number of hours past this month, your fragment is
	 * Calendar.MONTH. The result will be all hours of the past day(s).
	 * </p>
	 *
	 * <p>
	 * Valid fragments are: Calendar.YEAR, Calendar.MONTH, both Calendar.DAY_OF_YEAR
	 * and Calendar.DATE, Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND and
	 * Calendar.MILLISECOND A fragment less than or equal to a HOUR field will
	 * return 0.
	 * </p>
	 *
	 * <ul>
	 * <li>January 1, 2008 7:15:10.538 with Calendar.DAY_OF_YEAR as fragment will
	 * return 7 (equivalent to deprecated date.getHours())</li>
	 * <li>January 6, 2008 7:15:10.538 with Calendar.DAY_OF_YEAR as fragment will
	 * return 7 (equivalent to deprecated date.getHours())</li>
	 * <li>January 1, 2008 7:15:10.538 with Calendar.MONTH as fragment will return
	 * 7</li>
	 * <li>January 6, 2008 7:15:10.538 with Calendar.MONTH as fragment will return
	 * 127 (5*24 + 7)</li>
	 * <li>January 16, 2008 7:15:10.538 with Calendar.MILLISECOND as fragment will
	 * return 0 (a millisecond cannot be split in hours)</li>
	 * </ul>
	 *
	 * @param date     the date to work with, not null
	 * @param fragment the {@code Calendar} field part of date to calculate
	 * @return number of hours within the fragment of date
	 * @throws IllegalArgumentException if the date is {@code null} or fragment is
	 *                                  not supported
	 * @since 2.4
	 */
	public static long getFragmentInHours(final Date date, final int fragment) {
		return getFragment(date, fragment, TimeUnit.HOURS);
	}

	/**
	 * <p>
	 * Returns the number of days within the fragment. All datefields greater than
	 * the fragment will be ignored.
	 * </p>
	 *
	 * <p>
	 * Asking the days of any date will only return the number of days of the
	 * current month (resulting in a number between 1 and 31). This method will
	 * retrieve the number of days for any fragment. For example, if you want to
	 * calculate the number of days past this year, your fragment is Calendar.YEAR.
	 * The result will be all days of the past month(s).
	 * </p>
	 *
	 * <p>
	 * Valid fragments are: Calendar.YEAR, Calendar.MONTH, both Calendar.DAY_OF_YEAR
	 * and Calendar.DATE, Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND and
	 * Calendar.MILLISECOND A fragment less than or equal to a DAY field will return
	 * 0.
	 * </p>
	 *
	 * <ul>
	 * <li>January 28, 2008 with Calendar.MONTH as fragment will return 28
	 * (equivalent to deprecated date.getDay())</li>
	 * <li>February 28, 2008 with Calendar.MONTH as fragment will return 28
	 * (equivalent to deprecated date.getDay())</li>
	 * <li>January 28, 2008 with Calendar.YEAR as fragment will return 28</li>
	 * <li>February 28, 2008 with Calendar.YEAR as fragment will return 59</li>
	 * <li>January 28, 2008 with Calendar.MILLISECOND as fragment will return 0 (a
	 * millisecond cannot be split in days)</li>
	 * </ul>
	 *
	 * @param date     the date to work with, not null
	 * @param fragment the {@code Calendar} field part of date to calculate
	 * @return number of days within the fragment of date
	 * @throws IllegalArgumentException if the date is {@code null} or fragment is
	 *                                  not supported
	 * @since 2.4
	 */
	public static long getFragmentInDays(final Date date, final int fragment) {
		return getFragment(date, fragment, TimeUnit.DAYS);
	}

	/**
	 * <p>
	 * Returns the number of milliseconds within the fragment. All datefields
	 * greater than the fragment will be ignored.
	 * </p>
	 *
	 * <p>
	 * Asking the milliseconds of any date will only return the number of
	 * milliseconds of the current second (resulting in a number between 0 and 999).
	 * This method will retrieve the number of milliseconds for any fragment. For
	 * example, if you want to calculate the number of seconds past today, your
	 * fragment is Calendar.DATE or Calendar.DAY_OF_YEAR. The result will be all
	 * seconds of the past hour(s), minutes(s) and second(s).
	 * </p>
	 *
	 * <p>
	 * Valid fragments are: Calendar.YEAR, Calendar.MONTH, both Calendar.DAY_OF_YEAR
	 * and Calendar.DATE, Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND and
	 * Calendar.MILLISECOND A fragment less than or equal to a MILLISECOND field
	 * will return 0.
	 * </p>
	 *
	 * <ul>
	 * <li>January 1, 2008 7:15:10.538 with Calendar.SECOND as fragment will return
	 * 538 (equivalent to calendar.get(Calendar.MILLISECOND))</li>
	 * <li>January 6, 2008 7:15:10.538 with Calendar.SECOND as fragment will return
	 * 538 (equivalent to calendar.get(Calendar.MILLISECOND))</li>
	 * <li>January 6, 2008 7:15:10.538 with Calendar.MINUTE as fragment will return
	 * 10538 (10*1000 + 538)</li>
	 * <li>January 16, 2008 7:15:10.538 with Calendar.MILLISECOND as fragment will
	 * return 0 (a millisecond cannot be split in milliseconds)</li>
	 * </ul>
	 *
	 * @param calendar the calendar to work with, not null
	 * @param fragment the {@code Calendar} field part of calendar to calculate
	 * @return number of milliseconds within the fragment of date
	 * @throws IllegalArgumentException if the date is {@code null} or fragment is
	 *                                  not supported
	 * @since 2.4
	 */
	public static long getFragmentInMilliseconds(final Calendar calendar, final int fragment) {
		return getFragment(calendar, fragment, TimeUnit.MILLISECONDS);
	}

	/**
	 * <p>
	 * Returns the number of seconds within the fragment. All datefields greater
	 * than the fragment will be ignored.
	 * </p>
	 *
	 * <p>
	 * Asking the seconds of any date will only return the number of seconds of the
	 * current minute (resulting in a number between 0 and 59). This method will
	 * retrieve the number of seconds for any fragment. For example, if you want to
	 * calculate the number of seconds past today, your fragment is Calendar.DATE or
	 * Calendar.DAY_OF_YEAR. The result will be all seconds of the past hour(s) and
	 * minutes(s).
	 * </p>
	 *
	 * <p>
	 * Valid fragments are: Calendar.YEAR, Calendar.MONTH, both Calendar.DAY_OF_YEAR
	 * and Calendar.DATE, Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND and
	 * Calendar.MILLISECOND A fragment less than or equal to a SECOND field will
	 * return 0.
	 * </p>
	 *
	 * <ul>
	 * <li>January 1, 2008 7:15:10.538 with Calendar.MINUTE as fragment will return
	 * 10 (equivalent to calendar.get(Calendar.SECOND))</li>
	 * <li>January 6, 2008 7:15:10.538 with Calendar.MINUTE as fragment will return
	 * 10 (equivalent to calendar.get(Calendar.SECOND))</li>
	 * <li>January 6, 2008 7:15:10.538 with Calendar.DAY_OF_YEAR as fragment will
	 * return 26110 (7*3600 + 15*60 + 10)</li>
	 * <li>January 16, 2008 7:15:10.538 with Calendar.MILLISECOND as fragment will
	 * return 0 (a millisecond cannot be split in seconds)</li>
	 * </ul>
	 *
	 * @param calendar the calendar to work with, not null
	 * @param fragment the {@code Calendar} field part of calendar to calculate
	 * @return number of seconds within the fragment of date
	 * @throws IllegalArgumentException if the date is {@code null} or fragment is
	 *                                  not supported
	 * @since 2.4
	 */
	public static long getFragmentInSeconds(final Calendar calendar, final int fragment) {
		return getFragment(calendar, fragment, TimeUnit.SECONDS);
	}

	/**
	 * <p>
	 * Returns the number of minutes within the fragment. All datefields greater
	 * than the fragment will be ignored.
	 * </p>
	 *
	 * <p>
	 * Asking the minutes of any date will only return the number of minutes of the
	 * current hour (resulting in a number between 0 and 59). This method will
	 * retrieve the number of minutes for any fragment. For example, if you want to
	 * calculate the number of minutes past this month, your fragment is
	 * Calendar.MONTH. The result will be all minutes of the past day(s) and
	 * hour(s).
	 * </p>
	 *
	 * <p>
	 * Valid fragments are: Calendar.YEAR, Calendar.MONTH, both Calendar.DAY_OF_YEAR
	 * and Calendar.DATE, Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND and
	 * Calendar.MILLISECOND A fragment less than or equal to a MINUTE field will
	 * return 0.
	 * </p>
	 *
	 * <ul>
	 * <li>January 1, 2008 7:15:10.538 with Calendar.HOUR_OF_DAY as fragment will
	 * return 15 (equivalent to calendar.get(Calendar.MINUTES))</li>
	 * <li>January 6, 2008 7:15:10.538 with Calendar.HOUR_OF_DAY as fragment will
	 * return 15 (equivalent to calendar.get(Calendar.MINUTES))</li>
	 * <li>January 1, 2008 7:15:10.538 with Calendar.MONTH as fragment will return
	 * 15</li>
	 * <li>January 6, 2008 7:15:10.538 with Calendar.MONTH as fragment will return
	 * 435 (7*60 + 15)</li>
	 * <li>January 16, 2008 7:15:10.538 with Calendar.MILLISECOND as fragment will
	 * return 0 (a millisecond cannot be split in minutes)</li>
	 * </ul>
	 *
	 * @param calendar the calendar to work with, not null
	 * @param fragment the {@code Calendar} field part of calendar to calculate
	 * @return number of minutes within the fragment of date
	 * @throws IllegalArgumentException if the date is {@code null} or fragment is
	 *                                  not supported
	 * @since 2.4
	 */
	public static long getFragmentInMinutes(final Calendar calendar, final int fragment) {
		return getFragment(calendar, fragment, TimeUnit.MINUTES);
	}

	/**
	 * <p>
	 * Returns the number of hours within the fragment. All datefields greater than
	 * the fragment will be ignored.
	 * </p>
	 *
	 * <p>
	 * Asking the hours of any date will only return the number of hours of the
	 * current day (resulting in a number between 0 and 23). This method will
	 * retrieve the number of hours for any fragment. For example, if you want to
	 * calculate the number of hours past this month, your fragment is
	 * Calendar.MONTH. The result will be all hours of the past day(s).
	 * </p>
	 *
	 * <p>
	 * Valid fragments are: Calendar.YEAR, Calendar.MONTH, both Calendar.DAY_OF_YEAR
	 * and Calendar.DATE, Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND and
	 * Calendar.MILLISECOND A fragment less than or equal to a HOUR field will
	 * return 0.
	 * </p>
	 *
	 * <ul>
	 * <li>January 1, 2008 7:15:10.538 with Calendar.DAY_OF_YEAR as fragment will
	 * return 7 (equivalent to calendar.get(Calendar.HOUR_OF_DAY))</li>
	 * <li>January 6, 2008 7:15:10.538 with Calendar.DAY_OF_YEAR as fragment will
	 * return 7 (equivalent to calendar.get(Calendar.HOUR_OF_DAY))</li>
	 * <li>January 1, 2008 7:15:10.538 with Calendar.MONTH as fragment will return
	 * 7</li>
	 * <li>January 6, 2008 7:15:10.538 with Calendar.MONTH as fragment will return
	 * 127 (5*24 + 7)</li>
	 * <li>January 16, 2008 7:15:10.538 with Calendar.MILLISECOND as fragment will
	 * return 0 (a millisecond cannot be split in hours)</li>
	 * </ul>
	 *
	 * @param calendar the calendar to work with, not null
	 * @param fragment the {@code Calendar} field part of calendar to calculate
	 * @return number of hours within the fragment of date
	 * @throws IllegalArgumentException if the date is {@code null} or fragment is
	 *                                  not supported
	 * @since 2.4
	 */
	public static long getFragmentInHours(final Calendar calendar, final int fragment) {
		return getFragment(calendar, fragment, TimeUnit.HOURS);
	}

	/**
	 * <p>
	 * Returns the number of days within the fragment. All datefields greater than
	 * the fragment will be ignored.
	 * </p>
	 *
	 * <p>
	 * Asking the days of any date will only return the number of days of the
	 * current month (resulting in a number between 1 and 31). This method will
	 * retrieve the number of days for any fragment. For example, if you want to
	 * calculate the number of days past this year, your fragment is Calendar.YEAR.
	 * The result will be all days of the past month(s).
	 * </p>
	 *
	 * <p>
	 * Valid fragments are: Calendar.YEAR, Calendar.MONTH, both Calendar.DAY_OF_YEAR
	 * and Calendar.DATE, Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND and
	 * Calendar.MILLISECOND A fragment less than or equal to a DAY field will return
	 * 0.
	 * </p>
	 *
	 * <ul>
	 * <li>January 28, 2008 with Calendar.MONTH as fragment will return 28
	 * (equivalent to calendar.get(Calendar.DAY_OF_MONTH))</li>
	 * <li>February 28, 2008 with Calendar.MONTH as fragment will return 28
	 * (equivalent to calendar.get(Calendar.DAY_OF_MONTH))</li>
	 * <li>January 28, 2008 with Calendar.YEAR as fragment will return 28
	 * (equivalent to calendar.get(Calendar.DAY_OF_YEAR))</li>
	 * <li>February 28, 2008 with Calendar.YEAR as fragment will return 59
	 * (equivalent to calendar.get(Calendar.DAY_OF_YEAR))</li>
	 * <li>January 28, 2008 with Calendar.MILLISECOND as fragment will return 0 (a
	 * millisecond cannot be split in days)</li>
	 * </ul>
	 *
	 * @param calendar the calendar to work with, not null
	 * @param fragment the {@code Calendar} field part of calendar to calculate
	 * @return number of days within the fragment of date
	 * @throws IllegalArgumentException if the date is {@code null} or fragment is
	 *                                  not supported
	 * @since 2.4
	 */
	public static long getFragmentInDays(final Calendar calendar, final int fragment) {
		return getFragment(calendar, fragment, TimeUnit.DAYS);
	}

	/**
	 * Gets a Date fragment for any unit.
	 *
	 * @param date     the date to work with, not null
	 * @param fragment the Calendar field part of date to calculate
	 * @param unit     the time unit
	 * @return number of units within the fragment of the date
	 * @throws NullPointerException     if the date is {@code null}
	 * @throws IllegalArgumentException if fragment is not supported
	 * @since 2.4
	 */
	private static long getFragment(final Date date, final int fragment, final TimeUnit unit) {
		validateDateNotNull(date);
		final Calendar calendar = Calendar.getInstance();
		calendar.setTime(date);
		return getFragment(calendar, fragment, unit);
	}

	/**
	 * Gets a Calendar fragment for any unit.
	 *
	 * @param calendar the calendar to work with, not null
	 * @param fragment the Calendar field part of calendar to calculate
	 * @param unit     the time unit
	 * @return number of units within the fragment of the calendar
	 * @throws IllegalArgumentException if the date is {@code null} or fragment is
	 *                                  not supported
	 * @since 2.4
	 */
	private static long getFragment(final Calendar calendar, final int fragment, final TimeUnit unit) {
		if (calendar == null) {
			throw nullDateIllegalArgumentException();
		}

		long result = 0;

		final int offset = (unit == TimeUnit.DAYS) ? 0 : 1;

		// Fragments bigger than a day require a breakdown to days
		switch (fragment) {
		case Calendar.YEAR:
			result += unit.convert(calendar.get(Calendar.DAY_OF_YEAR) - offset, TimeUnit.DAYS);
			break;
		case Calendar.MONTH:
			result += unit.convert(calendar.get(Calendar.DAY_OF_MONTH) - offset, TimeUnit.DAYS);
			break;
		default:
			break;
		}

		switch (fragment) {
		// Number of days already calculated for these cases
		case Calendar.YEAR:
		case Calendar.MONTH:

			// The rest of the valid cases
		case Calendar.DAY_OF_YEAR:
		case Calendar.DATE:
			result += unit.convert(calendar.get(Calendar.HOUR_OF_DAY), TimeUnit.HOURS);
			//$FALL-THROUGH$
		case Calendar.HOUR_OF_DAY:
			result += unit.convert(calendar.get(Calendar.MINUTE), TimeUnit.MINUTES);
			//$FALL-THROUGH$
		case Calendar.MINUTE:
			result += unit.convert(calendar.get(Calendar.SECOND), TimeUnit.SECONDS);
			//$FALL-THROUGH$
		case Calendar.SECOND:
			result += unit.convert(calendar.get(Calendar.MILLISECOND), TimeUnit.MILLISECONDS);
			break;
		case Calendar.MILLISECOND:
			break; // never useful
		default:
			throw new IllegalArgumentException("The fragment " + fragment + " is not supported");
		}
		return result;
	}

	/**
	 * Determines if two calendars are equal up to no more than the specified most
	 * significant field.
	 *
	 * @param cal1  the first calendar, not {@code null}
	 * @param cal2  the second calendar, not {@code null}
	 * @param field the field from {@code Calendar}
	 * @return {@code true} if equal; otherwise {@code false}
	 * @throws IllegalArgumentException if any argument is {@code null}
	 * @see #truncate(Calendar, int)
	 * @see #truncatedEquals(Date, Date, int)
	 * @since 3.0
	 */
	public static boolean truncatedEquals(final Calendar cal1, final Calendar cal2, final int field) {
		return truncatedCompareTo(cal1, cal2, field) == 0;
	}

	/**
	 * Determines if two dates are equal up to no more than the specified most
	 * significant field.
	 *
	 * @param date1 the first date, not {@code null}
	 * @param date2 the second date, not {@code null}
	 * @param field the field from {@code Calendar}
	 * @return {@code true} if equal; otherwise {@code false}
	 * @throws IllegalArgumentException if any argument is {@code null}
	 * @see #truncate(Date, int)
	 * @see #truncatedEquals(Calendar, Calendar, int)
	 * @since 3.0
	 */
	public static boolean truncatedEquals(final Date date1, final Date date2, final int field) {
		return truncatedCompareTo(date1, date2, field) == 0;
	}

	/**
	 * Determines how two calendars compare up to no more than the specified most
	 * significant field.
	 *
	 * @param cal1  the first calendar, not {@code null}
	 * @param cal2  the second calendar, not {@code null}
	 * @param field the field from {@code Calendar}
	 * @return a negative integer, zero, or a positive integer as the first calendar
	 *         is less than, equal to, or greater than the second.
	 * @throws IllegalArgumentException if any argument is {@code null}
	 * @see #truncate(Calendar, int)
	 * @see #truncatedCompareTo(Date, Date, int)
	 * @since 3.0
	 */
	public static int truncatedCompareTo(final Calendar cal1, final Calendar cal2, final int field) {
		final Calendar truncatedCal1 = truncate(cal1, field);
		final Calendar truncatedCal2 = truncate(cal2, field);
		return truncatedCal1.compareTo(truncatedCal2);
	}

	/**
	 * Determines how two dates compare up to no more than the specified most
	 * significant field.
	 *
	 * @param date1 the first date, not {@code null}
	 * @param date2 the second date, not {@code null}
	 * @param field the field from {@code Calendar}
	 * @return a negative integer, zero, or a positive integer as the first date is
	 *         less than, equal to, or greater than the second.
	 * @throws IllegalArgumentException if any argument is {@code null}
	 * @see #truncate(Calendar, int)
	 * @see #truncatedCompareTo(Date, Date, int)
	 * @since 3.0
	 */
	public static int truncatedCompareTo(final Date date1, final Date date2, final int field) {
		final Date truncatedDate1 = truncate(date1, field);
		final Date truncatedDate2 = truncate(date2, field);
		return truncatedDate1.compareTo(truncatedDate2);
	}

	private static void validateDateNotNull(final Date date) {
		Validate.notNull(date, "date");
	}

	// -----------------------------------------------------------------------
	/**
	 * <p>
	 * Date iterator.
	 * </p>
	 */
	static class DateIterator implements Iterator<Calendar> {
		private final Calendar endFinal;
		private final Calendar spot;

		/**
		 * Constructs a DateIterator that ranges from one date to another.
		 *
		 * @param startFinal start date (inclusive)
		 * @param endFinal   end date (inclusive)
		 */
		DateIterator(final Calendar startFinal, final Calendar endFinal) {
			this.endFinal = endFinal;
			spot = startFinal;
			spot.add(Calendar.DATE, -1);
		}

		/**
		 * Has the iterator not reached the end date yet?
		 *
		 * @return {@code true} if the iterator has yet to reach the end date
		 */
		@Override
		public boolean hasNext() {
			return spot.before(endFinal);
		}

		/**
		 * Returns the next calendar in the iteration
		 *
		 * @return Object calendar for the next date
		 */
		@Override
		public Calendar next() {
			if (spot.equals(endFinal)) {
				throw new NoSuchElementException();
			}
			spot.add(Calendar.DATE, 1);
			return (Calendar) spot.clone();
		}

		/**
		 * Always throws UnsupportedOperationException.
		 *
		 * @throws UnsupportedOperationException Always thrown.
		 * @see java.util.Iterator#remove()
		 */
		@Override
		public void remove() {
			throw new UnsupportedOperationException();
		}
	}

}
