Further to the point first raised by Artur in
http://lists.wfu.edu/pipermail/gretl-devel/2019-February/009448.html
the $now accessor and the two closely related (complementary)
functions strftime() and strptime() are now documented, to a degree,
in git and snapshots.
As Jack said, the str*time() functions are maybe not very intuitive,
though they are quite standard (C, python, Ruby and R, among other,
support them). So if people wish to request more clarification and
examples, please so request. We want them to be usable!
Allin