Re: Two questions about thumbs.el

[Richard Stallman]

    time-less-p, time-subtract, time-add, time-to-days, time-to-day-in-year
    and date-leap-year-p are all documented on the *Time Calculations* node
    of the Emacs Lisp manual. It feels a bit weird to have one on subr.el
    and the rest on calendar/time-date.el

If time-less-p is used more often, it may be worth putting in subr.el.
But autoloading time-date.el will work too.  So another solution is
simply for the other packages to use time-less-p, with no other
change.