/* java.util.SimpleTimeZone
   Copyright (C) 1998, 1999, 2000, 2003, 2004, 2005  Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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any later version.

GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

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02111-1307 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
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this exception to your version of the library, but you are not
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exception statement from your version. */


package java.util;


/**
 * This class represents a simple time zone offset and handles
 * daylight savings.  It can only handle one daylight savings rule, so
 * it can't represent historical changes.
 *
 * This object is tightly bound to the Gregorian calendar.  It assumes
 * a regular seven days week, and the month lengths are that of the
 * Gregorian Calendar.  It can only handle daylight savings for years
 * lying in the AD era.
 *
 * @see Calendar
 * @see GregorianCalender
 * @author Jochen Hoenicke
 */
public class SimpleTimeZone extends TimeZone
{
  /**
   * The raw time zone offset in milliseconds to GMT, ignoring
   * daylight savings.
   * @serial
   */
  private int rawOffset;

  /**
   * True, if this timezone uses daylight savings, false otherwise.
   * @serial
   */
  private boolean useDaylight;

  /**
   * The daylight savings offset.  This is a positive offset in
   * milliseconds with respect to standard time.  Typically this
   * is one hour, but for some time zones this may be half an hour.
   * @serial
   * @since JDK1.1.4
   */
  private int dstSavings = 60 * 60 * 1000;

  /**
   * The first year, in which daylight savings rules applies.
   * @serial
   */
  private int startYear;
  private static final int DOM_MODE = 1;
  private static final int DOW_IN_MONTH_MODE = 2;
  private static final int DOW_GE_DOM_MODE = 3;
  private static final int DOW_LE_DOM_MODE = 4;

  /**
   * The mode of the start rule. This takes one of the following values:
   * <dl>
   * <dt>DOM_MODE (1)</dt>
   * <dd> startDay contains the day in month of the start date,
   * startDayOfWeek is unused. </dd>
   * <dt>DOW_IN_MONTH_MODE (2)</dt>
   * <dd> The startDay gives the day of week in month, and
   * startDayOfWeek the day of week.  For example startDay=2 and
   * startDayOfWeek=Calender.SUNDAY specifies that the change is on
   * the second sunday in that month.  You must make sure, that this
   * day always exists (ie. don't specify the 5th sunday).
   * </dd>
   * <dt>DOW_GE_DOM_MODE (3)</dt>
   * <dd> The start is on the first startDayOfWeek on or after
   * startDay.  For example startDay=13 and
   * startDayOfWeek=Calendar.FRIDAY specifies that the daylight
   * savings start on the first FRIDAY on or after the 13th of that
   * Month. Make sure that the change is always in the given month, or
   * the result is undefined.
   * </dd>
   * <dt>DOW_LE_DOM_MONTH (4)</dt>
   * <dd> The start is on the first startDayOfWeek on or before the
   * startDay.  Make sure that the change is always in the given
   * month, or the result is undefined.
   </dd>
   * </dl>
   * @serial */
  private int startMode;

  /**
   * The month in which daylight savings start.  This is one of the
   * constants Calendar.JANUARY, ..., Calendar.DECEMBER.
   * @serial
   */
  private int startMonth;

  /**
   * This variable can have different meanings.  See startMode for details
   * @see #startMode;
   * @serial
   */
  private int startDay;

  /**
   * This variable specifies the day of week the change takes place.  If
   * startMode == DOM_MODE, this is undefined.
   * @serial
   * @see #startMode;
   */
  private int startDayOfWeek;

  /**
   * This variable specifies the time of change to daylight savings.
   * This time is given in milliseconds after midnight local
   * standard time.
   * @serial
   */
  private int startTime;

  /**
   * This variable specifies the mode that startTime is specified in.  By
   * default it is WALL_TIME, but can also be STANDARD_TIME or UTC_TIME.  For
   * startTime, STANDARD_TIME and WALL_TIME are equivalent.
   * @serial
   */
  private int startTimeMode = WALL_TIME;

  /**
   * The month in which daylight savings ends.  This is one of the
   * constants Calendar.JANUARY, ..., Calendar.DECEMBER.
   * @serial
   */
  private int endMonth;

  /**
   * This variable gives the mode for the end of daylight savings rule.
   * It can take the same values as startMode.
   * @serial
   * @see #startMode
   */
  private int endMode;

  /**
   * This variable can have different meanings.  See startMode for details
   * @serial
   * @see #startMode;
   */
  private int endDay;

  /**
   * This variable specifies the day of week the change takes place.  If
   * endMode == DOM_MODE, this is undefined.
   * @serial
   * @see #startMode;
   */
  private int endDayOfWeek;

  /**
   * This variable specifies the time of change back to standard time.
   * This time is given in milliseconds after midnight local
   * standard time.
   * @serial
   */
  private int endTime;

  /**
   * This variable specifies the mode that endTime is specified in.  By
   * default it is WALL_TIME, but can also be STANDARD_TIME or UTC_TIME.
   * @serial
   */
  private int endTimeMode = WALL_TIME;

  /**
   * This variable points to a deprecated array from JDK 1.1.  It is
   * ignored in JDK 1.2 but streamed out for compatibility with JDK 1.1.
   * The array contains the lengths of the months in the year and is
   * assigned from a private static final field to avoid allocating
   * the array for every instance of the object.
   * Note that static final fields are not serialized.
   * @serial
   */
  private byte[] monthLength = monthArr;
  private static final byte[] monthArr = 
                                         {
                                           31, 28, 31, 30, 31, 30, 31, 31, 30,
                                           31, 30, 31
                                         };

  /**
   * The version of the serialized data on the stream.
   * <dl>
   * <dt>0 or not present on stream</dt>
   * <dd> JDK 1.1.3 or earlier, only provides this fields:
   * rawOffset, startDay, startDayOfWeek, startMonth, startTime,
   * startYear, endDay, endDayOfWeek, endMonth, endTime
   * </dd>
   * <dd> JDK 1.1.4 or later. This includes three new fields, namely
   * startMode, endMode and dstSavings.  And there is a optional section
   * as described in writeObject.
   * </dd>
   * </dl>
   *
   * XXX - JDK 1.2 Beta 4 docu states 1.1.4, but my 1.1.5 has the old
   * version.
   *
   * When streaming out this class it is always written in the latest
   * version.
   * @serial
   * @since JDK1.1.4
   */
  private int serialVersionOnStream = 2;
  private static final long serialVersionUID = -403250971215465050L;

  /**
   * Constant to indicate that start and end times are specified in standard
   * time, without adjusting for daylight savings.
   */
  public static final int STANDARD_TIME = 1;

  /**
   * Constant to indicate that start and end times are specified in wall
   * time, adjusting for daylight savings.  This is the default.
   */
  public static final int WALL_TIME = 0;

  /**
   * Constant to indicate that start and end times are specified in UTC.
   */
  public static final int UTC_TIME = 2;

  /**
   * Create a <code>SimpleTimeZone</code> with the given time offset
   * from GMT and without daylight savings.
   * @param rawOffset the time offset from GMT in milliseconds.
   * @param id The identifier of this time zone.
   */
  public SimpleTimeZone(int rawOffset, String id)
  {
    this.rawOffset = rawOffset;
    setID(id);
    useDaylight = false;
    startYear = 0;
  }

  /**
   * Create a <code>SimpleTimeZone</code> with the given time offset
   * from GMT and with daylight savings.  The start/end parameters
   * can have different meaning (replace WEEKDAY with a real day of
   * week). Only the first two meanings were supported by earlier
   * versions of jdk.
   *
   * <dl>
   * <dt><code>day &gt; 0, dayOfWeek = Calendar.WEEKDAY</code></dt>
   * <dd>The start/end of daylight savings is on the <code>day</code>-th
   * <code>WEEKDAY</code> in the given month. </dd>
   * <dt><code>day &lt; 0, dayOfWeek = Calendar.WEEKDAY</code></dt>
   * <dd>The start/end of daylight savings is on the <code>-day</code>-th
   * <code>WEEKDAY</code> counted from the <i>end</i> of the month. </dd>
   * <dt><code>day &gt; 0, dayOfWeek = 0</code></dt>
   * <dd>The start/end of daylight is on the <code>day</code>-th day of
   * the month. </dd>
   * <dt><code>day &gt; 0, dayOfWeek = -Calendar.WEEKDAY</code></dt>
   * <dd>The start/end of daylight is on the first WEEKDAY on or after
   * the <code>day</code>-th day of the month.  You must make sure that
   * this day lies in the same month. </dd>
   * <dt><code>day &lt; 0, dayOfWeek = -Calendar.WEEKDAY</code></dt>
   * <dd>The start/end of daylight is on the first WEEKDAY on or
   * <i>before</i> the <code>-day</code>-th day of the month.  You
   * must make sure that this day lies in the same month. </dd>
   * </dl>
   *
   * If you give a non existing month, a day that is zero, or too big,
   * or a dayOfWeek that is too big,  the result is undefined.
   *
   * The start rule must have a different month than the end rule.
   * This restriction shouldn't hurt for all possible time zones.
   *
   * @param rawOffset The time offset from GMT in milliseconds.
   * @param id  The identifier of this time zone.
   * @param startMonth The start month of daylight savings; use the
   * constants in Calendar.
   * @param startday A day in month or a day of week number, as
   * described above.
   * @param startDayOfWeek The start rule day of week; see above.
   * @param startTime A time in millis in standard time.
   * @param endMonth The end month of daylight savings; use the
   * constants in Calendar.
   * @param endday A day in month or a day of week number, as
   * described above.
   * @param endDayOfWeek The end rule day of week; see above.
   * @param endTime A time in millis in standard time.
   * @throws IllegalArgumentException if parameters are invalid or out of
   * range.
   */
  public SimpleTimeZone(int rawOffset, String id, int startMonth,
                        int startDayOfWeekInMonth, int startDayOfWeek,
                        int startTime, int endMonth, int endDayOfWeekInMonth,
                        int endDayOfWeek, int endTime)
  {
    this.rawOffset = rawOffset;
    setID(id);
    useDaylight = true;

    setStartRule(startMonth, startDayOfWeekInMonth, startDayOfWeek, startTime);
    setEndRule(endMonth, endDayOfWeekInMonth, endDayOfWeek, endTime);
    if (startMonth == endMonth)
      throw new IllegalArgumentException("startMonth and endMonth must be different");
    this.startYear = 0;
  }

  /**
   * This constructs a new SimpleTimeZone that supports a daylight savings
   * rule.  The parameter are the same as for the constructor above, except
   * there is the additional dstSavaings parameter.
   *
   * @param dstSavings the amount of savings for daylight savings
   * time in milliseconds.  This must be positive.
   * @since 1.2
   */
  public SimpleTimeZone(int rawOffset, String id, int startMonth,
                        int startDayOfWeekInMonth, int startDayOfWeek,
                        int startTime, int endMonth, int endDayOfWeekInMonth,
                        int endDayOfWeek, int endTime, int dstSavings)
  {
    this(rawOffset, id, startMonth, startDayOfWeekInMonth, startDayOfWeek,
         startTime, endMonth, endDayOfWeekInMonth, endDayOfWeek, endTime);

    this.dstSavings = dstSavings;
  }

  /**
   * This constructs a new SimpleTimeZone that supports a daylight savings
   * rule.  The parameter are the same as for the constructor above, except
   * there are the additional startTimeMode, endTimeMode, and dstSavings
   * parameters.
   *
   * @param startTimeMode the mode that start times are specified in.  One of
   * WALL_TIME, STANDARD_TIME, or UTC_TIME.
   * @param endTimeMode the mode that end times are specified in.  One of
   * WALL_TIME, STANDARD_TIME, or UTC_TIME.
   * @param dstSavings the amount of savings for daylight savings
   * time in milliseconds.  This must be positive.
   * @throws IllegalArgumentException if parameters are invalid or out of
   * range.
   * @since 1.4
   */
  public SimpleTimeZone(int rawOffset, String id, int startMonth,
                        int startDayOfWeekInMonth, int startDayOfWeek,
                        int startTime, int startTimeMode, int endMonth,
                        int endDayOfWeekInMonth, int endDayOfWeek,
                        int endTime, int endTimeMode, int dstSavings)
  {
    this.rawOffset = rawOffset;
    setID(id);
    useDaylight = true;

    if (startTimeMode < WALL_TIME || startTimeMode > UTC_TIME)
      throw new IllegalArgumentException("startTimeMode must be one of WALL_TIME, STANDARD_TIME, or UTC_TIME");
    if (endTimeMode < WALL_TIME || endTimeMode > UTC_TIME)
      throw new IllegalArgumentException("endTimeMode must be one of WALL_TIME, STANDARD_TIME, or UTC_TIME");
    this.startTimeMode = startTimeMode;
    this.endTimeMode = endTimeMode;

    setStartRule(startMonth, startDayOfWeekInMonth, startDayOfWeek, startTime);
    setEndRule(endMonth, endDayOfWeekInMonth, endDayOfWeek, endTime);
    if (startMonth == endMonth)
      throw new IllegalArgumentException("startMonth and endMonth must be different");
    this.startYear = 0;

    this.dstSavings = dstSavings;
  }

  /**
   * Sets the first year, where daylight savings applies.  The daylight
   * savings rule never apply for years in the BC era.  Note that this
   * is gregorian calendar specific.
   * @param year the start year.
   */
  public void setStartYear(int year)
  {
    startYear = year;
    useDaylight = true;
  }

  /**
   * Checks if the month, day, dayOfWeek arguments are in range and
   * returns the mode of the rule.
   * @param month the month parameter as in the constructor
   * @param day the day parameter as in the constructor
   * @param dayOfWeek the day of week parameter as in the constructor
   * @return the mode of this rule see startMode.
   * @exception IllegalArgumentException if parameters are out of range.
   * @see #SimpleTimeZone(int, String, int, int, int, int, int, int, int, int)
   * @see #startMode
   */
  private int checkRule(int month, int day, int dayOfWeek)
  {
    if (month < 0 || month > 11)
      throw new IllegalArgumentException("month out of range");

    int daysInMonth = getDaysInMonth(month, 1);
    if (dayOfWeek == 0)
      {
	if (day <= 0 || day > daysInMonth)
	  throw new IllegalArgumentException("day out of range");
	return DOM_MODE;
      }
    else if (dayOfWeek > 0)
      {
	if (Math.abs(day) > (daysInMonth + 6) / 7)
	  throw new IllegalArgumentException("dayOfWeekInMonth out of range");
	if (dayOfWeek > Calendar.SATURDAY)
	  throw new IllegalArgumentException("dayOfWeek out of range");
	return DOW_IN_MONTH_MODE;
      }
    else
      {
	if (day == 0 || Math.abs(day) > daysInMonth)
	  throw new IllegalArgumentException("day out of range");
	if (dayOfWeek < -Calendar.SATURDAY)
	  throw new IllegalArgumentException("dayOfWeek out of range");
	if (day < 0)
	  return DOW_LE_DOM_MODE;
	else
	  return DOW_GE_DOM_MODE;
      }
  }

  /**
   * Sets the daylight savings start rule.  You must also set the
   * end rule with <code>setEndRule</code> or the result of
   * getOffset is undefined.  For the parameters see the ten-argument
   * constructor above.
   *
   * @param month The month where daylight savings start, zero
   * based.  You should use the constants in Calendar.
   * @param day A day of month or day of week in month.
   * @param dayOfWeek The day of week where daylight savings start.
   * @param time The time in milliseconds standard time where daylight
   * savings start.
   * @see SimpleTimeZone
   */
  public void setStartRule(int month, int day, int dayOfWeek, int time)
  {
    this.startMode = checkRule(month, day, dayOfWeek);
    this.startMonth = month;
    this.startDay = day;
    this.startDayOfWeek = Math.abs(dayOfWeek);
    if (this.startTimeMode == WALL_TIME || this.startTimeMode == STANDARD_TIME)
      this.startTime = time;
    else
      // Convert from UTC to STANDARD
      this.startTime = time + this.rawOffset;
    useDaylight = true;
  }

  /**
   * Sets the daylight savings start rule.  You must also set the
   * end rule with <code>setEndRule</code> or the result of
   * getOffset is undefined.  For the parameters see the ten-argument
   * constructor above.
   *
   * Note that this API isn't incredibly well specified.  It appears that the
   * after flag must override the parameters, since normally, the day and
   * dayofweek can select this.  I.e., if day < 0 and dayOfWeek < 0, on or
   * before mode is chosen.  But if after == true, this implementation
   * overrides the signs of the other arguments.  And if dayOfWeek == 0, it
   * falls back to the behavior in the other APIs.  I guess this should be
   * checked against Sun's implementation.
   *
   * @param month The month where daylight savings start, zero
   * based.  You should use the constants in Calendar.
   * @param day A day of month or day of week in month.
   * @param dayOfWeek The day of week where daylight savings start.
   * @param time The time in milliseconds standard time where daylight
   * savings start.
   * @param after If true, day and dayOfWeek specify first day of week on or
   * after day, else first day of week on or before.
   * @since 1.2
   * @see SimpleTimeZone
   */
  public void setStartRule(int month, int day, int dayOfWeek, int time,
                           boolean after)
  {
    // FIXME: XXX: Validate that checkRule and offset processing work with on
    // or before mode.
    this.startDay = after ? Math.abs(day) : -Math.abs(day);
    this.startDayOfWeek = after ? Math.abs(dayOfWeek) : -Math.abs(dayOfWeek);
    this.startMode = (dayOfWeek != 0)
                     ? (after ? DOW_GE_DOM_MODE : DOW_LE_DOM_MODE)
                     : checkRule(month, day, dayOfWeek);
    this.startDay = Math.abs(this.startDay);
    this.startDayOfWeek = Math.abs(this.startDayOfWeek);

    this.startMonth = month;

    if (this.startTimeMode == WALL_TIME || this.startTimeMode == STANDARD_TIME)
      this.startTime = time;
    else
      // Convert from UTC to STANDARD
      this.startTime = time + this.rawOffset;
    useDaylight = true;
  }

  /**
   * Sets the daylight savings start rule.  You must also set the
   * end rule with <code>setEndRule</code> or the result of
   * getOffset is undefined.  For the parameters see the ten-argument
   * constructor above.
   *
   * @param month The month where daylight savings start, zero
   * based.  You should use the constants in Calendar.
   * @param day A day of month or day of week in month.
   * @param time The time in milliseconds standard time where daylight
   * savings start.
   * @see SimpleTimeZone
   * @since 1.2
   */
  public void setStartRule(int month, int day, int time)
  {
    setStartRule(month, day, 0, time);
  }

  /**
   * Sets the daylight savings end rule.  You must also set the
   * start rule with <code>setStartRule</code> or the result of
   * getOffset is undefined. For the parameters see the ten-argument
   * constructor above.
   *
   * @param month The end month of daylight savings.
   * @param day A day in month, or a day of week in month.
   * @param dayOfWeek A day of week, when daylight savings ends.
   * @param time A time in millis in standard time.
   * @see #setStartRule
   */
  public void setEndRule(int month, int day, int dayOfWeek, int time)
  {
    this.endMode = checkRule(month, day, dayOfWeek);
    this.endMonth = month;
    this.endDay = day;
    this.endDayOfWeek = Math.abs(dayOfWeek);
    if (this.endTimeMode == WALL_TIME)
      this.endTime = time;
    else if (this.endTimeMode == STANDARD_TIME)
      // Convert from STANDARD to DST
      this.endTime = time + this.dstSavings;
    else
      // Convert from UTC to DST
      this.endTime = time + this.rawOffset + this.dstSavings;
    useDaylight = true;
  }

  /**
   * Sets the daylight savings end rule.  You must also set the
   * start rule with <code>setStartRule</code> or the result of
   * getOffset is undefined. For the parameters see the ten-argument
   * constructor above.
   *
   * Note that this API isn't incredibly well specified.  It appears that the
   * after flag must override the parameters, since normally, the day and
   * dayofweek can select this.  I.e., if day < 0 and dayOfWeek < 0, on or
   * before mode is chosen.  But if after == true, this implementation
   * overrides the signs of the other arguments.  And if dayOfWeek == 0, it
   * falls back to the behavior in the other APIs.  I guess this should be
   * checked against Sun's implementation.
   *
   * @param month The end month of daylight savings.
   * @param day A day in month, or a day of week in month.
   * @param dayOfWeek A day of week, when daylight savings ends.
   * @param time A time in millis in standard time.
   * @param after If true, day and dayOfWeek specify first day of week on or
   * after day, else first day of week on or before.
   * @since 1.2
   * @see #setStartRule
   */
  public void setEndRule(int month, int day, int dayOfWeek, int time,
                         boolean after)
  {
    // FIXME: XXX: Validate that checkRule and offset processing work with on
    // or before mode.
    this.endDay = after ? Math.abs(day) : -Math.abs(day);
    this.endDayOfWeek = after ? Math.abs(dayOfWeek) : -Math.abs(dayOfWeek);
    this.endMode = (dayOfWeek != 0)
                   ? (after ? DOW_GE_DOM_MODE : DOW_LE_DOM_MODE)
                   : checkRule(month, day, dayOfWeek);
    this.endDay = Math.abs(this.endDay);
    this.endDayOfWeek = Math.abs(endDayOfWeek);

    this.endMonth = month;

    if (this.endTimeMode == WALL_TIME)
      this.endTime = time;
    else if (this.endTimeMode == STANDARD_TIME)
      // Convert from STANDARD to DST
      this.endTime = time + this.dstSavings;
    else
      // Convert from UTC to DST
      this.endTime = time + this.rawOffset + this.dstSavings;
    useDaylight = true;
  }

  /**
   * Sets the daylight savings end rule.  You must also set the
   * start rule with <code>setStartRule</code> or the result of
   * getOffset is undefined. For the parameters see the ten-argument
   * constructor above.
   *
   * @param month The end month of daylight savings.
   * @param day A day in month, or a day of week in month.
   * @param dayOfWeek A day of week, when daylight savings ends.
   * @param time A time in millis in standard time.
   * @see #setStartRule
   */
  public void setEndRule(int month, int day, int time)
  {
    setEndRule(month, day, 0, time);
  }

  /**
   * Gets the time zone offset, for current date, modified in case of
   * daylight savings.  This is the offset to add to UTC to get the local
   * time.
   *
   * In the standard JDK the results given by this method may result in
   * inaccurate results at the end of February or the beginning of March.
   * To avoid this, you should use Calendar instead:
   * <code>offset = cal.get(Calendar.ZONE_OFFSET)
   * + cal.get(Calendar.DST_OFFSET);</code>
   *
   * This version doesn't suffer this inaccuracy.
   *
   * The arguments don't follow the approach for setting start and end rules.
   * The day must be a positive number and dayOfWeek must be a positive value
   * from Calendar.  dayOfWeek is redundant, but must match the other values
   * or an inaccurate result may be returned.
   *
   * @param era the era of the given date
   * @param year the year of the given date
   * @param month the month of the given date, 0 for January.
   * @param day the day of month
   * @param dayOfWeek the day of week; this must match the other fields.
   * @param millis the millis in the day (in local standard time)
   * @return the time zone offset in milliseconds.
   * @throws IllegalArgumentException if arguments are incorrect.
   */
  public int getOffset(int era, int year, int month, int day, int dayOfWeek,
                       int millis)
  {
    int daysInMonth = getDaysInMonth(month, year);
    if (day < 1 || day > daysInMonth)
      throw new IllegalArgumentException("day out of range");
    if (dayOfWeek < Calendar.SUNDAY || dayOfWeek > Calendar.SATURDAY)
      throw new IllegalArgumentException("dayOfWeek out of range");
    if (month < Calendar.JANUARY || month > Calendar.DECEMBER)
      throw new IllegalArgumentException("month out of range:" + month);

    // This method is called by Calendar, so we mustn't use that class.
    int daylightSavings = 0;
    if (useDaylight && era == GregorianCalendar.AD && year >= startYear)
      {
	// This does only work for Gregorian calendars :-(
	// This is mainly because setStartYear doesn't take an era.
	boolean afterStart = ! isBefore(year, month, day, dayOfWeek, millis,
	                                startMode, startMonth, startDay,
	                                startDayOfWeek, startTime);
	boolean beforeEnd = isBefore(year, month, day, dayOfWeek,
				     millis + dstSavings,
	                             endMode, endMonth, endDay, endDayOfWeek,
	                             endTime);

	if (startMonth < endMonth)
	  // use daylight savings, if the date is after the start of
	  // savings, and before the end of savings.
	  daylightSavings = afterStart && beforeEnd ? dstSavings : 0;
	else
	  // use daylight savings, if the date is before the end of
	  // savings, or after the start of savings.
	  daylightSavings = beforeEnd || afterStart ? dstSavings : 0;
      }
    return rawOffset + daylightSavings;
  }

  /**
   * Returns the time zone offset to GMT in milliseconds, ignoring
   * day light savings.
   * @return the time zone offset.
   */
  public int getRawOffset()
  {
    return rawOffset;
  }

  /**
   * Sets the standard time zone offset to GMT.
   * @param rawOffset The time offset from GMT in milliseconds.
   */
  public void setRawOffset(int rawOffset)
  {
    this.rawOffset = rawOffset;
  }

  /**
   * Gets the daylight savings offset.  This is a positive offset in
   * milliseconds with respect to standard time.  Typically this
   * is one hour, but for some time zones this may be half an our.
   * @return the daylight savings offset in milliseconds.
   *
   * @since 1.2
   */
  public int getDSTSavings()
  {
    return dstSavings;
  }

  /**
   * Sets the daylight savings offset.  This is a positive offset in
   * milliseconds with respect to standard time.
   *
   * @param dstSavings the daylight savings offset in milliseconds.
   *
   * @since 1.2
   */
  public void setDSTSavings(int dstSavings)
  {
    if (dstSavings <= 0)
      throw new IllegalArgumentException("illegal value for dstSavings");

    this.dstSavings = dstSavings;
  }

  /**
   * Returns if this time zone uses daylight savings time.
   * @return true, if we use daylight savings time, false otherwise.
   */
  public boolean useDaylightTime()
  {
    return useDaylight;
  }

  /**
   * Returns the number of days in the given month.
   * Uses gregorian rules prior to 1582 (The default and earliest cutover)
   * @param month The month, zero based; use one of the Calendar constants.
   * @param year  The year.
   */
  private int getDaysInMonth(int month, int year)
  {
    if (month == Calendar.FEBRUARY)
      {
	if ((year & 3) != 0)
	  return 28;

	// Assume default Gregorian cutover, 
	// all years prior to this must be Julian
	if (year < 1582)
	  return 29;

	// Gregorian rules 
	return ((year % 100) != 0 || (year % 400) == 0) ? 29 : 28;
      }
    else
      return monthArr[month];
  }

  /**
   * Checks if the date given in calXXXX, is before the change between
   * dst and standard time.
   * @param calYear the year of the date to check (for leap day checking).
   * @param calMonth the month of the date to check.
   * @param calDay the day of month of the date to check.
   * @param calDayOfWeek the day of week of the date to check.
   * @param calMillis the millis of day of the date to check (standard time).
   * @param mode  the change mode; same semantic as startMode.
   * @param month the change month; same semantic as startMonth.
   * @param day   the change day; same semantic as startDay.
   * @param dayOfWeek the change day of week;
   * @param millis the change time in millis since midnight standard time.
   * same semantic as startDayOfWeek.
   * @return true, if cal is before the change, false if cal is on
   * or after the change.
   */
  private boolean isBefore(int calYear, int calMonth, int calDayOfMonth,
                           int calDayOfWeek, int calMillis, int mode,
                           int month, int day, int dayOfWeek, int millis)
  {
    // This method is called by Calendar, so we mustn't use that class.
    // We have to do all calculations by hand.
    // check the months:
    // XXX - this is not correct:
    // for the DOW_GE_DOM and DOW_LE_DOM modes the change date may
    // be in a different month.
    if (calMonth != month)
      return calMonth < month;

    // check the day:
    switch (mode)
      {
      case DOM_MODE:
	if (calDayOfMonth != day)
	  return calDayOfMonth < day;
	break;
      case DOW_IN_MONTH_MODE:
        {
	  // This computes the day of month of the day of type
	  // "dayOfWeek" that lies in the same (sunday based) week as cal.
	  calDayOfMonth += (dayOfWeek - calDayOfWeek);

	  // Now we convert it to 7 based number (to get a one based offset
	  // after dividing by 7).  If we count from the end of the
	  // month, we get want a -7 based number counting the days from 
	  // the end:
	  if (day < 0)
	    calDayOfMonth -= getDaysInMonth(calMonth, calYear) + 7;
	  else
	    calDayOfMonth += 6;

	  //  day > 0                    day < 0
	  //  S  M  T  W  T  F  S        S  M  T  W  T  F  S
	  //     7  8  9 10 11 12         -36-35-34-33-32-31
	  // 13 14 15 16 17 18 19      -30-29-28-27-26-25-24
	  // 20 21 22 23 24 25 26      -23-22-21-20-19-18-17
	  // 27 28 29 30 31 32 33      -16-15-14-13-12-11-10
	  // 34 35 36                   -9 -8 -7
	  // Now we calculate the day of week in month:
	  int week = calDayOfMonth / 7;

	  //  day > 0                    day < 0
	  //  S  M  T  W  T  F  S        S  M  T  W  T  F  S
	  //     1  1  1  1  1  1          -5 -5 -4 -4 -4 -4
	  //  1  2  2  2  2  2  2       -4 -4 -4 -3 -3 -3 -3
	  //  2  3  3  3  3  3  3       -3 -3 -3 -2 -2 -2 -2
	  //  3  4  4  4  4  4  4       -2 -2 -2 -1 -1 -1 -1
	  //  4  5  5                   -1 -1 -1
	  if (week != day)
	    return week < day;

	  if (calDayOfWeek != dayOfWeek)
	    return calDayOfWeek < dayOfWeek;

	  // daylight savings starts/ends  on the given day.
	  break;
        }
      case DOW_LE_DOM_MODE:
	// The greatest sunday before or equal December, 12
	// is the same as smallest sunday after or equal December, 6.
	day = Math.abs(day) - 6;
      case DOW_GE_DOM_MODE:
	// Calculate the day of month of the day of type
	// "dayOfWeek" that lies before (or on) the given date.
	calDayOfMonth -= (calDayOfWeek < dayOfWeek ? 7 : 0) + calDayOfWeek
	- dayOfWeek;
	if (calDayOfMonth < day)
	  return true;
	if (calDayOfWeek != dayOfWeek || calDayOfMonth >= day + 7)
	  return false;

	// now we have the same day
	break;
      }

    // the millis decides:
    return (calMillis < millis);
  }

  /**
   * Determines if the given date is in daylight savings time.
   * @return true, if it is in daylight savings time, false otherwise.
   */
  public boolean inDaylightTime(Date date)
  {
    Calendar cal = Calendar.getInstance(this);
    cal.setTime(date);
    return (cal.get(Calendar.DST_OFFSET) != 0);
  }

  /**
   * Generates the hashCode for the SimpleDateFormat object.  It is
   * the rawOffset, possibly, if useDaylightSavings is true, xored
   * with startYear, startMonth, startDayOfWeekInMonth, ..., endTime.
   */
  public synchronized int hashCode()
  {
    return rawOffset
           ^ (useDaylight
              ? startMonth ^ startDay ^ startDayOfWeek ^ startTime ^ endMonth
              ^ endDay ^ endDayOfWeek ^ endTime : 0);
  }

  public synchronized boolean equals(Object o)
  {
    if (this == o)
      return true;
    if (! (o instanceof SimpleTimeZone))
      return false;
    SimpleTimeZone zone = (SimpleTimeZone) o;
    if (zone.hashCode() != hashCode() || ! getID().equals(zone.getID())
        || rawOffset != zone.rawOffset || useDaylight != zone.useDaylight)
      return false;
    if (! useDaylight)
      return true;
    return (startYear == zone.startYear && startMonth == zone.startMonth
           && startDay == zone.startDay
           && startDayOfWeek == zone.startDayOfWeek
           && startTime == zone.startTime
           && startTimeMode == zone.startTimeMode && endMonth == zone.endMonth
           && endDay == zone.endDay && endDayOfWeek == zone.endDayOfWeek
           && endTime == zone.endTime && endTimeMode == zone.endTimeMode);
  }

  /**
   * Test if the other time zone uses the same rule and only
   * possibly differs in ID.  This implementation for this particular
   * class will return true if the other object is a SimpleTimeZone,
   * the raw offsets and useDaylight are identical and if useDaylight
   * is true, also the start and end datas are identical.
   * @return true if this zone uses the same rule.
   */
  public boolean hasSameRules(TimeZone other)
  {
    if (this == other)
      return true;
    if (! (other instanceof SimpleTimeZone))
      return false;
    SimpleTimeZone zone = (SimpleTimeZone) other;
    if (zone.hashCode() != hashCode() || rawOffset != zone.rawOffset
        || useDaylight != zone.useDaylight)
      return false;
    if (! useDaylight)
      return true;
    return (startYear == zone.startYear && startMonth == zone.startMonth
           && startDay == zone.startDay
           && startDayOfWeek == zone.startDayOfWeek
           && startTime == zone.startTime
           && startTimeMode == zone.startTimeMode && endMonth == zone.endMonth
           && endDay == zone.endDay && endDayOfWeek == zone.endDayOfWeek
           && endTime == zone.endTime && endTimeMode == zone.endTimeMode);
  }

  /**
   * Returns a string representation of this SimpleTimeZone object.
   * @return a string representation of this SimpleTimeZone object.
   */
  public String toString()
  {
    // the test for useDaylight is an incompatibility to jdk1.2, but
    // I think this shouldn't hurt.
    return getClass().getName() + "[" + "id=" + getID() + ",offset="
           + rawOffset + ",dstSavings=" + dstSavings + ",useDaylight="
           + useDaylight
           + (useDaylight
              ? ",startYear=" + startYear + ",startMode=" + startMode
              + ",startMonth=" + startMonth + ",startDay=" + startDay
              + ",startDayOfWeek=" + startDayOfWeek + ",startTime="
              + startTime + ",startTimeMode=" + startTimeMode + ",endMode="
              + endMode + ",endMonth=" + endMonth + ",endDay=" + endDay
              + ",endDayOfWeek=" + endDayOfWeek + ",endTime=" + endTime
              + ",endTimeMode=" + endTimeMode : "") + "]";
  }

  /**
   * Reads a serialized simple time zone from stream.
   * @see #writeObject
   */
  private void readObject(java.io.ObjectInputStream input)
    throws java.io.IOException, ClassNotFoundException
  {
    input.defaultReadObject();
    if (serialVersionOnStream == 0)
      {
	// initialize the new fields to default values.
	dstSavings = 60 * 60 * 1000;
	endMode = DOW_IN_MONTH_MODE;
	startMode = DOW_IN_MONTH_MODE;
	startTimeMode = WALL_TIME;
	endTimeMode = WALL_TIME;
	serialVersionOnStream = 2;
      }
    else
      {
	int length = input.readInt();
	byte[] byteArray = new byte[length];
	input.read(byteArray, 0, length);
	if (length >= 4)
	  {
	    // Lets hope that Sun does extensions to the serialized
	    // form in a sane manner.
	    startDay = byteArray[0];
	    startDayOfWeek = byteArray[1];
	    endDay = byteArray[2];
	    endDayOfWeek = byteArray[3];
	  }
      }
  }

  /**
   * Serializes this object to a stream.  @serialdata The object is
   * first written in the old JDK 1.1 format, so that it can be read
   * by by the old classes.  This means, that the
   * <code>start/endDay(OfWeek)</code>-Fields are written in the
   * DOW_IN_MONTH_MODE rule, since this was the only supported rule
   * in 1.1.
   *
   * In the optional section, we write first the length of an byte
   * array as int and afterwards the byte array itself.  The byte
   * array contains in this release four elements, namely the real
   * startDay, startDayOfWeek endDay, endDayOfWeek in that Order.
   * These fields are needed, because for compatibility reasons only
   * approximative values are written to the required section, as
   * described above.
   */
  private void writeObject(java.io.ObjectOutputStream output)
    throws java.io.IOException
  {
    byte[] byteArray = new byte[]
                       {
                         (byte) startDay, (byte) startDayOfWeek, (byte) endDay,
                         (byte) endDayOfWeek
                       };

    /* calculate the approximation for JDK 1.1 */
    switch (startMode)
      {
      case DOM_MODE:
	startDayOfWeek = Calendar.SUNDAY; // random day of week

      // fall through
      case DOW_GE_DOM_MODE:
      case DOW_LE_DOM_MODE:
	startDay = (startDay + 6) / 7;
      }
    switch (endMode)
      {
      case DOM_MODE:
	endDayOfWeek = Calendar.SUNDAY;

      // fall through
      case DOW_GE_DOM_MODE:
      case DOW_LE_DOM_MODE:
	endDay = (endDay + 6) / 7;
      }

    // the required part:
    output.defaultWriteObject();
    // the optional part:
    output.writeInt(byteArray.length);
    output.write(byteArray, 0, byteArray.length);
  }
}