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Diffstat (limited to 'proginfo/timezone.txt')
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diff --git a/proginfo/timezone.txt b/proginfo/timezone.txt new file mode 100644 index 0000000..7868093 --- /dev/null +++ b/proginfo/timezone.txt @@ -0,0 +1,85 @@ +Timezone strings: +----------------- +This is a description of valid timezone strings for ENV[ARC]:TZ: +"XPG3TZ - time zone information" +The form of the time zone information is based on the XPG3 specification of +the TZ environment variable. Spaces are allowed only in timezone +designations, where they are significant. The following description +closely follows the XPG3 specification, except for the paragraphs starting +**CLARIFICATION**. + +<std><offset>[<dst>[<offset>],<start>[/<time>],<end>[/<time>]] + +Where: +<std> and <dst> + Are each three or more bytes that are the designation for the + standard (<std>) and daylight savings time (<dst>) timezones. + Only <std> is required - if <dst> is missing, then daylight + savings time does not apply in this locale. Upper- and + lower-case letters are allowed. Any characters except a + leading colon (:), digits, a comma (,), a minus (-) or a plus + (+) are allowed. + **CLARIFICATION** The two-byte designation `UT' is permitted. +<offset> + Indicates the value one must add to the local time to arrive + at Coordinated Universal Time. The offset has the form: + <hh>[:<mm>[:<ss>]] + The minutes <mm> and seconds <ss> are optional. The hour <hh> + is required and may be a single digit. The offset following + <std> is required. If no offset follows <dst>, daylight savings + time is assumed to be one hour ahead of standard time. One or + more digits may be used; the value is always interpreted as a + decimal number. The hour must be between 0 and 24, and the + minutes (and seconds) if present between 0 and 59. Out of + range values may cause unpredictable behavior. If preceded by + a `-', the timezone is east of the Prime Meridian; otherwise + it is west (which may be indicated by an optional preceding + `+' sign). + **CLARIFICATION** No more than two digits are allowed in any + of <hh>, <mm> or <ss>. Leading zeros are permitted. +<start>/<time> and <end>/<time> + Indicates when to change to and back from daylight savings + time, where <start>/<time> describes when the change from + standard time to daylight savings time occurs, and + <end>/<time> describes when the change back happens. Each + <time> field describes when, in current local time, the change + is made. + **CLARIFICATION** It is recognized that in the Southern + hemisphere <start> will specify a date later than <end>. + The formats of <start> and <end> are one of the following: + J<n> The Julian day <n> (1 <= <n> <= 365). Leap days are not + counted. That is, in all years, February 28 is day 59 + and March 1 is day 60. It is impossible to refer to + the occasional February 29. + <n> The zero-based Julian day (0 <= <n> <= 365). Leap days + are counted, and it is possible to refer to February + 29. + M<m>.<n>.<d> + The <d>th day, (0 <= <d> <= 6) of week <n> of month <m> + of the year (1 <= <n> <= 5, 1 <= <m> <= 12), where week + 5 means `the last <d>-day in month <m>' (which may + occur in either the fourth or the fifth week). Week 1 + is the first week in which the <d>th day occurs. Day + zero is Sunday. + **CLARIFICATION** Neither <n> nor <m> may have a + leading zero. <d> must be a single digit. + **CLARIFICATION** The default <start> and <end> values + are from the first Sunday in April until the last Sunday + in October. This allows United States users to leave out + the <start> and <end> parts, as most are accustomed to + doing. + <time> has the same format as <offset> except that no leading + sign (`-' or `+') is allowed. The default, if <time> is not + given is 02:00:00. + **CLARIFICATION** The number of hours in <time> may be up + to 167, to allow encoding of rules such as `00:00hrs on the + Sunday after the second Friday in September' + +Example (for Central Europe): +----------------------------- +MET-1MEST,M3.5.0,M10.5.0/03 + +Another example, for the US East Coast: +--------------------------------------- +EST5EDT4,M4.1.0/02,M10.5.0/02 +This string describes the default values when no time zone is set. |