cal-persia.el disagrees with Iranian calendar in A.D. 2025

[Paul Eggert]

Roozbeh Pournader <roozbeh at farsiweb.info> writes:

> The text of the Iranian law, in effect since 1925, clearly mentions
> that the true solar year is the measure, and there is no arithmetic
> leap year calculation involved.  There has never been any serious
> plan to change that law....

Thanks for making this clear.  I'll update the tz database
accordingly; the only year this affects in the current database is
2025 Gregorian (both spring and fall transitions).  I'll add Oscar's
comments for years after 2037, as a warning to future maintainers.

> I'm not sure about Birashk's suggested leap year rule ... but a very
> simpler one I checked (using 33-year cycles) will not differ from
> the astronomical one until sometime in the 2070s.

This suggests that cal-persia.el could be changed as well, as its
practical use is (I think) for predicting dates in Iran.  I'm hesitant
to propose a change myself, though, as I'm not an expert in either the
calendar or the code.