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Babel

The multilingual framework to localize LaTeX, LuaLaTeX, XeLaTeX

What’s new in babel 3.76

2022-06-06

Calendars

Although calendars aren’t the primary concern of babel, the package should be able to, at least, generate correctly \today in the way users would expect in their own culture. Currently, \localedate can print dates in a few calendars (provided the ini locale file has been imported), but year, month and day had to be entered by hand, which is very inconvenient.

Until now, babel provided just the Hebrew calendar with hebcal.sty, which shows how cumbersome can be the required computations with pure TeX. Now, thanks to the l3fp library, they are quite straightforward.

There are converters for 3 calendars:

Hebrew. Basically the set of TeX macros written by Rozman in 1991, with corrections and adaptations by Porrat, Misha, Haran and Lavva. This must be eventually replaced by computations with l3fp.

Islamic. Two calendar are defined: islamic-civil (arithmetical) and islamic-umalqura. The code for the former has been taken from calendar.js by John Walker (public domain). The Umm al-Qura calendar, used mainly in Saudi Arabia, is based on moment-hijri (by Abdullah Alsigar, license MIT). Since the main aim is to provide a suitable \today, and maybe some close dates, data for islamic-umalqura just cover Hijri ~1435/~1460 (Gregorian ~2014/~2038). They can be adjusted with +, - after the name (and ++, -- in the Civil calendar), so that, for example, with islamic-civil+ a day is added.

Persian. There is an algorithm written in TeX by Jabri, Abolhassani, Pournader and Esfahbod, created for the first versions of the FarsiTeX system (no longer available), but the original license is GPL, so its use with LPPL is problematic. The code here follows loosely that by John Walker (see above), which is free and accurate, but sadly very complex, so the relevant data for the years 2013-2050 have been pre-calculated and stored. Actually, all we need is the first day of the Jalali year (either March 20 or March 21).

An example is:

\babelcalendar[2020-04-01]{islamic-civil}{\iyear}{\imonth}{\iday}
\localedate[calendar=islamic]{\iyear}{\imonth}{\iday}

Without the optional argument the current date is used.

Of course new tools will be devised to configure the locales when they are loaded, to set the default \today.

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