[BUG] Date prompt suggests yesterday when changing timestamp with org-extend-today-until set [9.6]

[Tim Ruffing <crypto@timruffing.de>]

Hi,

Assume org-extend-today-until is set to an integer greater 0, say 3.
When I change a timestamp without date such as <2023-01-20> (e.g, when
rescheduling), the prompt defaults to a day earlier, i.e., to "2023-01-
19" in this case. The same happens with <2023-01-20 01:00> which is
still before 3am. 
 
That's very confusing, in particular in the case when the old timestamp
only has a date but no time. But even when the old timestamp has has a
time, org should never suggest yesterday. I think a good rule of thumb
here is that if the user just presses Enter without having typed
anything at the prompt, the timestamp shouldn't change at all.

The bug happens because org-read-date tries to take into account the
value of org-extend-today-until but it should probably do this when the
default time suggested to the user is taken from the current wallclock
time, not when it's taken from an existing timestamp. 

A similar issue when capturing has been reported and fixed here:
https://lists.gnu.org/archive/html/emacs-orgmode/2019-06/msg00056.html

(Please include me in CC for now, I haven't subscribed to mailing
list.) 

Best,
Tim


PS: Thanks for org-mode. It has my changed my life.