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