From: Farley Flud <fsquared@fsquared.linux>
Subject: Re: Microsoft to force new Outlook on Windows 10 PCs
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Date: Fri, 17 Jan 2025 13:03:08 +0000
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On Thu, 16 Jan 2025 14:40:22 -0600, Physfitfreak wrote:

> I wrote programs on them that I'm still using today! 
> For one, a calendar conversion program I wrote handled conversions 
> between Iranian lunar, Iranian solar, the Gregorian and before that the 
> Julian solar dates nicely. Maximum error just one day! And you could go 
> back in time even to the days of Darius if you insisted, cause I also 
> took into account the precession of the Earth's rotational axis. I know 
> of no calendar inversion software (accessible to public) that does that. 
> They'll get even the season wrong if you go back that far, let alone the 
> day.
> 

I believe that Julian Dates (JD) are used for this purpose.  The JD
is a count of the number of days since January 1, 4713 BCE.

The next step would be to convert the JD to a particular solar or
lunar calendar.

GNU/Linux has complete JD facilities.

I am not sure how the GNU/Linux "cal" command would handle historic
dates before the Julian calendar, which was introduced in 45 BCE. 
But I am investigating this issue now because it is, to me, a very
interesting one.

I do know that cal can handle accurately dates during that bizarre
period of Julian-to-Gregorian transition.




-- 
Hail Linux!  Hail FOSS!  Hail Stallman!