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From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: getFirstDayOfMonth()
Date: Wed, 13 Mar 2024 08:47:17 -0700
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Spiros Bousbouras <spibou@gmail.com> writes:
> On Wed, 13 Mar 2024 06:01:22 +0100
> jak <nospam@please.ty> wrote:
>> Instead, I would be curious to understand why nobody follows a standard
>> about the dates. Let's take this date for example: January 1, 1580.
>> On the web 50% of the sites searched with "day of week calculator" say
>> that the day was Tuesday while the others say it was Friday. Excel and
>> Calc (OpenOffice) say it was Friday and the same says "cal" on *nix if
>> the "--iso" option is not used. So, someone follows the ISO convention
>> and others Julian but I read somewhere that the ISO convention had to be
>> followed in the computer scope.
>
> For the year 1580 what would be the appropriate standard ? I don't see any
> point using a modern standard for 1580. The day of the week is a cultural
> matter depending on era and location so what useful cultural information
> would you get by knowing that according to a modern standard , January 1
> 1580 was whatever day ?

There's something called the proleptic Gregorian calendar, produced by
extending the rules for the Gregorian calendar back to dates preceding
its introduction.  It's used fairly widely.

https://en.wikipedia.org/wiki/Proleptic_Gregorian_calendar

Note also that in the US consider George Washington's birthday is
considered to be February 22 (NS, new style), even though that date was
February 11 (OS) under the Julian calender then in effect.

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for Medtronic
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