On 26/04/2022 16:07, Ihor Radchenko wrote:
> 
> LGTM. I think you can go ahead and continue with the followup patch
> making use of the new macro.

The attached patch set is assumed to be complete.

I have no chance to thoroughly test it. Existing unit tests pass for 
Emacs-26 and Emacs-27. Nothing has changed for Emacs-25, as for the 
"main" branch one test fails. I have not tried Emacs-28 or the current 
git version.

In comparison to the previous patch version I have expanded the 
docstring and added a bit more tests. I have tried to support recently 
committed to Emacs 6-elements list for `encode-time', but I do not like 
the following compile-time warning:

> In toplevel form:
> org-macs.el:1397:23:Warning: encode-time called with 1 argument, but requires
>     6+

I had to carve the patch originally posted by Paul Eggert for the Emacs 
repository to adapt it for the Org repository and to drop 
org-encode-time-1 chunks.
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=54764#10

The largest patch replaces all calls of `encode-time' to `org-encode-time'

Goals of `org-encode-time':
- it should work at the compile or load time to minimize runtime 
performance impact,
- since both ways to call `encode-time' are necessary (in a half of 
cases a list returned by `decode-time' is available, in other cases 
timestamps are assembled from scratch, none is preferred), it should be 
convenient in both cases,
- it should allow Org to work even if support of multiple `encode-time' 
arguments will be removed from Emacs,
- it should allow to avoid a pitfall with Emacs-27+ `encode-time': DST 
argument is taken into account when the function called with single list 
argument but it is ignored when multiple arguments is passed. 
`org-encode-time' respects DST value unless it is running in Emacs-26 or 
earlier. I have not added special code for old versions considering it 
as graceful degradation.

Finally, let me remind that these changes are result of the following 
discussions:

Ignacio Casso to emacs-orgmode. [BUG] org-agenda thinks timestamps after 
23:00 correspond to the next day.  Tue, 29 Mar 2022 15:09:10 +0200. 
https://list.orgmode.org/PAXPR06MB7760238F410CBE3203F78EE0C61E9@PAXPR06MB7760.eurprd06.prod.outlook.com

https://debbugs.gnu.org/cgi/bugreport.cgi?bug=54731
https://list.orgmode.org/8b85c879-4f9b-eac3-e700-f176cc588577@gmail.com
#54731 - Please, revert part of dd0727e1ec1 related to Org mode 
(`encode-time') - GNU bug report logs

https://debbugs.gnu.org/cgi/bugreport.cgi?bug=54764
https://list.orgmode.org/5ed963b2-3fa8-48d8-627e-bc0571d15b43@gmail.com
#54764 - encode-time: make DST and TIMEZONE fields of the list argument 
optional ones - GNU bug report logs