Hi Bruno, Bruno Haible via Gnulib discussion list <bug-gnulib@gnu.org> writes:
> This patch adds proper support for the non-Gregorian calendars in use in > - Thailand, > - Iran, > - Ethiopia, > to the 'nstrftime' module and, with it (automatically) to the GNU coreutils > 'date' program (for output). > > Why is this needed? Because these countries don't use the Gregorian calendar > primarily. > > * Thailand: > https://en.wikipedia.org/wiki/Thai_calendar says > "In Thailand, two main calendar systems are used alongside each other: > the Thai solar calendar, based on the Gregorian calendar and used for > official and most day-to-day purposes, and ..." > > * Iran: > https://en.wikipedia.org/wiki/Solar_Hijri_calendar says > "The Solar Hijri calendar is the official calendar of Iran." > https://en.wikipedia.org/wiki/Solar_Hijri_calendar#Iran says > "The present Iranian calendar was legally adopted on 31 March 1925" > > https://en.wikipedia.org/wiki/Iranian_calendars#Modern_calendar:_Solar_Hijri_(SH) > says "The present Iranian calendar was legally adopted on 31 March 1925" > > * Ethiopia: > https://en.wikipedia.org/wiki/Ethiopian_calendar says it > "is the official state civil calendar of Ethiopia". [...] > > The ISO C 23 § 7.29.3.5 and POSIX > https://pubs.opengroup.org/onlinepubs/9799919799/functions/strftime.html > specifications specify an "alternative" choice feature. This code does > *NOT* make use of this "alternative" API. > It's better if the use of the specific calendar turns on the > particular years, months names and numbers, days etc. all at once. > Rationale: > - Because the "alternatives" approach that makes it too easy to produce > nonsensical output (as shown with %Y in the Thai locale, above). > - Because there is no documentation anywhere what "alternative" actually > means. > - Because in ISO C and POSIX the month number is specified to be in the > range 1..12, but some calendars (the Ethiopian calendar) have month > numbers 1..13. > - Because the month number to month name mapping may depend on the era > in some calendars (the Thai calendar). > > So, the code is careful not to mix Gregorian time elements (in 'struct tm') > with non-Gregorian time elements (in 'struct calendar_date'). > > Pádraig, you may add something like the following as a coreutils/NEWS entry: > > 'date' now outputs dates in the country's native calendar for the Iranian > locale (fa_IR) and for the Ethiopian locale (am_ET), and also does so more > consistently for the Thailand locale (th_TH.UTF-8). Thank you for the interesting patch and explaining your reasonings. I was going to write some tests for Coreutils, but had second thoughts about this change after reading the POSIX documentation for 'date' [1]: The date string formatting capabilities are intended for use in Gregorian-style calendars, possibly with a different starting year (or years). The %x and %c conversion specifications, however, are intended for local representation; these may be based on a different, non-Gregorian calendar. This is under APPLICATION USAGE, so not normative. But I think that most people will assume that 'date' will return a Gregorian calendar date, unless they explicitly use "%x" or "%c". I think it would be good to support non-Gregorian calendars with those format arguments, or a new option. But making it the default will just require some users to remember to change their locale when posting the output of 'date' in communication with foreigners (e.g. on a mailing list). As you mentioned, in Thailand the Gregorian calendar is used alongside the Thai solar calendar (even if it is used less so in day-to-day life). And the Ethiopian calendar has been a cause for confusion as the world becomes more globalized [2]. I assume this was part of the reason Saudi Arabia moved to the Gregorian Calendar in 2016 (although most of the articles I found cited saving 11 days of yearly pay per government employee) [3]. Collin [1] https://pubs.opengroup.org/onlinepubs/9799919799/utilities/date.html [2] https://www.cnn.com/travel/ethiopian-unique-calendar-year [3] https://www.economist.com/middle-east-and-africa/2016/12/15/saudi-arabia-adopts-the-gregorian-calendar
