On 23 Aug 2024, at 21:08, Paul Eggert via austin-group-l at The Open Group [off-list ref] wrote:

On 2024-08-23 10:48, Alejandro Colomar wrote:

quoted

Robert, Geoff, Andrew, can you please clarify where is the discussion
that led to the following change?:

Why does it matter? The tm_wday idea has worked everywhere for decades and is now standardized.

For what it's worth, GNU Emacs has been using the tm_wday idea since 2018, when I made the following change:

I am a bit curious about the original discussion, which I cannot see:

I have recently brushed up a C++ program I wrote that uses the Julian Day Number (JDN) and Julian date, which is used in astronomy. So, for example, 0 JDN, the Julian calendar date -4712-01-01, is a Monday, making it easy to find the day of the week, computing modulo 7. The Julian date 0.0 is noon UT on 0 JDN.

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