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- 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** If <dst> is given then <start>
- and <end> are required - there is no `implementation
- specific default'.
-
- <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 Germany):
- ----------------------
-
- MET-1MEST,M3.5.0,M9.5.0/03
-