Ciao Mohammad I believe the Persian calendar system is likely the most astronomically accurate of currently used calendar systems.
Its based on observation, unlike Gregorian which is based on rules. https://www.timeanddate.com/calendar/persian-calendar.html Just a comment TT On Monday, 13 April 2020 08:25:08 UTC+2, Mohammad wrote: > > Example Calendar system: Persian Calendar > > Like the Gregorian <https://www.projectpluto.com/calendar.htm#gregorian> > and Julian <https://www.projectpluto.com/calendar.htm#julian>calendars, > the Persian calendar is strictly solar in nature; that is, it matches the > seasons very nicely (better, in fact, than any other calendar on these > pages), but makes no real effort to reflect lunar cycles. There are twelve > months per year, as follows. > > farvardin (frvrdyn) 31 days > ordibehesht (ardybhSt) 31 days > khordad (Krdad) 31 days > tir (tyr) 31 days > mordad (mrdad) 31 days > shahrivar (Shryvr) 31 days > mehr (mhr) 30 days > Aban (Aban) 30 days > Azar (AZr) 30 days > day (dy) 30 days > bahman (bhmn) 30 days > esfand (asfnd) 29/30 days > > The year begins at the spring equinox. If that instant is before midday, > Teheran time, then that day is 1 farvardin; otherwise, the next day is 1 > farvardin. This can result in either 365 or 366 days per year. In the > former (usual) case, the last month of esfand has 29 days; otherwise, it > has 30 days. > > The Jalali calendar uses the "exact" astronomical equinox; that is to say, > it's based on observations. The Modern Persian calendar instead inserts > leap years algorithmically, with a complex pattern of 683 leap days > inserted over a cycle of 2820 years. This actually makes the Modern Persian > calendar extremely easy to program (see the source code described here.) > <https://www.projectpluto.com/source.htm#date_cpp>The Jalali calendar is > a little trickier, as will be discussed below. > -- You received this message because you are subscribed to the Google Groups "TiddlyWiki" group. To unsubscribe from this group and stop receiving emails from it, send an email to tiddlywiki+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/tiddlywiki/2a7b982a-009b-409b-9aa3-cc05cbc08490%40googlegroups.com.
