Re: date %d day question

[Jeffrey Walton]

On Wed, Oct 30, 2024 at 1:42 AM Tapani Tarvainen
<bash@tapanitarvainen.fi> wrote:
>
> On Tue, Oct 29, 2024 at 08:43:37PM -0400, Greg Wooledge (greg@wooledge.org) 
> wrote:
>
> > February has 28 days, except in "leap years", where it has 29 days.
>
> > The estimate of "every 4th year" was used before the Gregorian calendar,
> > and it turned out to be noticeably wrong.  The adjustment to remove 3
> > leap years every 400 years is what differentiates the Gregorian calendar
> > from the Julian calendar that was used previously.
>
> Yes. An amusing anecdote: Sweden decided to switch to the Gregorian
> calendar in 1700, but to minimize confusion, they decided to move
> adjust the calendar gradually, one day at a time every four years, and
> started by skipping February 29 on 1700. They failed to follow up in
> the following years however, and by 1711 they realized it was not a
> good idea to begin with, as their calendar was out of sync with
> everybody.
>
> Then instead of jumping ahead they decided to go back to the Julian
> calendar, and they did so by having an extra leap day on 1712, making
> it a 367-day year with February 30.
>
> As far as I know it's the only occurrence of February 30 anywhere.

The Soviet Union had a February 30, too:
<https://www.timeanddate.com/date/february-30.html>.

Jeff