pike.git / lib / modules / Calendar.pmod / tzdata / Theory

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pike.git/lib/modules/Calendar.pmod/tzdata/Theory:166:   remaining data.         ----- Time zone abbreviations -----      When this package is installed, it generates time zone abbreviations   like 'EST' to be compatible with human tradition and POSIX.   Here are the general rules used for choosing time zone abbreviations,   in decreasing order of importance:    -  Use abbreviations that consist of three or more ASCII letters. +  Use three or more characters that are ASCII alphanumerics or '+' or '-'.    Previous editions of this database also used characters like    ' ' and '?', but these characters have a special meaning to    the shell and cause commands like    set `date`    to have unexpected effects.    Previous editions of this rule required upper-case letters,    but the Congressman who introduced Chamorro Standard Time -  preferred "ChST", so the rule has been relaxed. -  -  This rule guarantees that all abbreviations could have -  been specified by a POSIX TZ string. POSIX -  requires at least three characters for an -  abbreviation. POSIX through 2000 says that an abbreviation -  cannot start with ':', and cannot contain ',', '-', -  '+', NUL, or a digit. POSIX from 2001 on changes this -  rule to say that an abbreviation can contain only '-', '+', +  preferred "ChST", so lower-case letters are now allowed. +  Also, POSIX from 2001 on relaxed the rule to allow '-', '+',    and alphanumeric characters from the portable character set -  in the current locale. To be portable to both sets of -  rules, an abbreviation must therefore use only ASCII -  letters. +  in the current locale. In practice ASCII alphanumerics and +  '+' and '-' are safe in all locales.    -  +  In other words, in the C locale the POSIX extended regular +  expression [-+[:alnum:]]{3,} should match the abbreviation. +  This guarantees that all abbreviations could have been +  specified by a POSIX TZ string. +     Use abbreviations that are in common use among English-speakers,    e.g. 'EST' for Eastern Standard Time in North America.    We assume that applications translate them to other languages    as part of the normal localization process; for example,    a French application might translate 'EST' to 'HNE'.       For zones whose times are taken from a city's longitude, use the    traditional xMT notation, e.g. 'PMT' for Paris Mean Time.    The only name like this in current use is 'GMT'.