Add support for dealing with decoded time structures

* doc/lispref/os.texi (Time Conversion): Document the new
functions that work on decoded time.
(Time Calculations): Document new date/time functions.

* lisp/simple.el (decoded-time-second, decoded-time-minute)
(decoded-time-hour, decoded-time-day, decoded-time-month)
(decoded-time-year, decoded-time-weekday, decoded-time-dst)
(decoded-time-zone): New accessor functions for decoded time values.

* lisp/calendar/time-date.el (date-days-in-month)
(date-ordinal-to-time): New functions.
(decoded-time--alter-month, decoded-time--alter-day)
(decoded-time--alter-second, make-decoded-time): New functions
added to manipulate decoded time structures.

* src/timefns.c (Fdecode_time): Mention the new accessors.

* test/lisp/calendar/time-date-tests.el: New file to test the
decoded time functions and the other new functions.

1 files changed, 15 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index c654b9ba34a..2bdbfcb8d08 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -2069,6 +2069,21 @@ that acts like the '0' flag but also puts a '+' before nonnegative
 years containing more than four digits.  This is for compatibility
 with POSIX.1-2017.
 
++++
+*** To access (or alter) the elements a decoded time value, the
+'decoded-time-second', 'decoded-time-minute', 'decoded-time-hour',
+'decoded-time-day', 'decoded-time-month', 'decoded-time-year',
+'decoded-time-weekday', 'decoded-time-dst' and 'decoded-time-zone'
+accessors can be used.
+
++++
+*** The new functions `date-days-in-month' (which will say how many
+days there are in a month in a specific year), `date-ordinal-to-time'
+(that computes the date of an ordinal day), `decoded-time-add' for
+doing computations on a decoded time structure), and
+`make-decoded-time' (for making a decoded time structure with only the
+given keywords filled out) have been added.
+
 ** 'define-minor-mode' automatically documents the meaning of ARG.
 
 +++