DESCRIPTIONA time zone is unambiguously defined by the set of time measurement rules determined by the governing body for a given geographic area. These rules describe at a minimum the base offset from UTC for the time zone, often referred to as the Standard Time offset. Many locations adjust their Standard Time forward or backward by one hour, in order to accommodate seasonal changes in number of daylight hours, often referred to as Daylight Saving Time. Some locations adjust their time by a fraction of an hour. Standard Time is also known as Winter Time. Daylight Saving Time is also known as Advanced Time, Summer Time, or Legal Time in certain countries. The following table shows the changes in time zone rules in effect for New York City starting from 1967. Each line represents a description or rule for a particular observance.
Effective Observance Rule Date (Date/Time) Offset Abbreviation 1967-* last Sun in Oct, 02:00 -0500 EST 1967-1973 last Sun in Apr, 02:00 -0400 EDT 1974-1974 Jan 6, 02:00 -0400 EDT 1975-1975 Feb 23, 02:00 -0400 EDT 1976-1986 last Sun in Apr, 02:00 -0400 EDT 1987-* first Sun in Apr, 02:00 -0400 EDT
Note: The specification of a global time zone registry is not addressed by this document and is left for future study. However, implementers may find the Olson time zone database [TZ] a useful reference. It is an informal, public-domain collection of time zone information, which is currently being maintained by volunteer Internet participants, and is used in several operating systems. This database contains current and historical time zone information for a wide variety of locations around the globe; it provides a time zone identifier for every unique time zone rule set in actual use since 1970, with historical data going back to the introduction of standard time.
ical_entry_typeReturns "DAYLIGHT", its iCalendar entry name.
mandatory_unique_propertiesAccording to the iCalendar standard, the following properties must be specified exactly one time in a daylight declaration:
dtstart tzoffsetto tzoffsetfrom
optional_repeatable_propertiesAccording to the iCalendar standard, the following properties may be specified any number of times for a daylight declaration:
comment rdate rrule tzname
AUTHORBest Practical Solutions, LLC <[email protected]>
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This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself. See perlartistic.