[HC Evolution] Review of Calendar docs

[Ali Abdin <aliabdin aucegypt edu>]

Okay - I just skimmed over JWZ's links to the calendar docs
http://emr.cs.uiuc.edu/~reingold/calendar.ps
http://emr.cs.uiuc.edu/~reingold/calendar2.ps

I'm still on calendar.ps and I read the Islamic part. Very informative -
and it /seems/ sooo simple. Yes it is implementable in that state. But
there is something that i'm going to quote:
Page 11 (out of 30):
It is important to realize that, to some extent, the above calculations are
merely
hypothetical because there are many disparate forms of the Islamic
calendar. 4 Fur­thermore, much of the Islamic world relies not on such
calculations at all, but on
proclamation of the new moon by religious authorities. Consequently, the
dates given  by the Lisp function here can be in error by a day or two from
what will actually be observed in various parts of the Islamic world; this
is unavoidable.


So how do evolution hackers want to go from here. To overcome this
'out-of-sync' that can occur, I propose that Evolution ships "the current
date" during this Islamic year. (which will remain accurate for the next 9
months). Secondly I propose a user-config option that would allow them to
'sync' the gregorian (really time_t) and the Islamic dates together (so
when the date does change - the user can adjust himself). Of course - this
causes the 'scheduling' problem - but i think we can cross that bridge when
we come to it.

An even 'better' solution is to give Evolution the ability to 'sync up'
with an on-line Islamic date thingy (provided by Helix Code?) so the user
doesn't have to mess (and possibly screw around) the dates.

I also just read the 'holidays' section. Very good stuff (for
implementation) No comments except for the fact that these dates can 'also
be inaccurate' according to the docs (and me). See the 'sync up' comments
above :)

calendar2.pas turns out to be a discussion of old/ancient calendars :)
Doesn't interest me (or you?)

Comments? Please :)


Ali Abdin

P.S. There is a 'mistake' in the docs. To my belief the Islamic day does
not /begin/ at sunset. In the real world we use normal time. Religious
events (such as prayer times, fasting etc) are based on sunrise and
sunset - but these aren't really important.