[bug#74689] [PATCH] Add predicates for decoded times and time deltas

[Paul Eggert]

What's the use case for these proposed predicates? I'm finding it hard 
to review the patch without knowing what it's for.

Surely this should be in time-date.el rather than simple.el.

The implementation of decoded-time-p seems complicated and doesn't match 
what decode-time produces. Wouldn't it be simpler to call (ignore-errors 
(equal val (decode-time (encode-time val))))?