SimpleTimeZone is a concrete subclass of TimeZone that represents a time zone for use with a Gregorian calendar. The class holds an offset from GMT, called raw offset, and start and end rules for a daylight saving time schedule. Since it only holds single values for each, it cannot handle historical changes in the offset from GMT and the daylight saving schedule, except that the setStartYear method can specify the year when the daylight saving time schedule starts in effect.

To construct a SimpleTimeZone with a daylight saving time schedule, the schedule can be described with a set of rules, start-rule and end-rule. A day when daylight saving time starts or ends is specified by a combination of month, day-of-month, and day-of-week values. The month value is represented by a Calendar MONTH field value, such as MARCH . The day-of-week value is represented by a Calendar DAY_OF_WEEK value, such as SUNDAY . The meanings of value combinations are as follows.

• Exact day of month
  To specify an exact day of month, set the month and day-of-month to an exact value, and day-of-week to zero. For example, to specify March 1, set the month to MARCH , day-of-month to 1, and day-of-week to 0.
• Day of week on or after day of month
  To specify a day of week on or after an exact day of month, set the month to an exact month value, day-of-month to the day on or after which the rule is applied, and day-of-week to a negative DAY_OF_WEEK field value. For example, to specify the second Sunday of April, set month to APRIL , day-of-month to 8, and day-of-week to - SUNDAY .
• Day of week on or before day of month
  To specify a day of the week on or before an exact day of the month, set day-of-month and day-of-week to a negative value. For example, to specify the last Wednesday on or before the 21st of March, set month to MARCH , day-of-month is -21 and day-of-week is - WEDNESDAY .
• Last day-of-week of month
  To specify, the last day-of-week of the month, set day-of-week to a DAY_OF_WEEK value and day-of-month to -1. For example, to specify the last Sunday of October, set month to OCTOBER , day-of-week to SUNDAY and day-of-month to -1.

The time of the day at which daylight saving time starts or ends is specified by a millisecond value within the day. There are three kinds of modes to specify the time: WALL_TIME , STANDARD_TIME and UTC_TIME . For example, if daylight saving time ends at 2:00 am in the wall clock time, it can be specified by 7200000 milliseconds in the WALL_TIME mode. In this case, the wall clock time for an end-rule means the same thing as the daylight time.

The following are examples of parameters for constructing time zone objects.

      // Base GMT offset: -8:00
      // DST starts:      at 2:00am in standard time
      //                  on the first Sunday in April
      // DST ends:        at 2:00am in daylight time
      //                  on the last Sunday in October
      // Save:            1 hour
      SimpleTimeZone(-28800000,
                     "America/Los_Angeles",
                     Calendar.APRIL, 1, -Calendar.SUNDAY,
                     7200000,
                     Calendar.OCTOBER, -1, Calendar.SUNDAY,
                     7200000,
                     3600000)

      // Base GMT offset: +1:00
      // DST starts:      at 1:00am in UTC time
      //                  on the last Sunday in March
      // DST ends:        at 1:00am in UTC time
      //                  on the last Sunday in October
      // Save:            1 hour
      SimpleTimeZone(3600000,
                     "Europe/Paris",
                     Calendar.MARCH, -1, Calendar.SUNDAY,
                     3600000, SimpleTimeZone.UTC_TIME,
                     Calendar.OCTOBER, -1, Calendar.SUNDAY,
                     3600000, SimpleTimeZone.UTC_TIME,
                     3600000)
 

These parameter rules are also applicable to the set rule methods, such as setStartRule.