>
> While this topic is raised, would it make sense for Org-mode table
> formula to automatically parse any time-like string into time units
> (i.e., base sixty).  That would be the easiest for most users, and (I
> imagine) would rarely result in surprising and unexpected behavior.
>

So, I took a shot at folding this into org-table.el, the resulting patch
is attached.  I'm not sure if this sort of automatic interpretation of
time-like strings into integers is a good idea, or if this is the best
implementation (I'm not incredibly familiar with Org's table handling)
but after a couple of simple tests the patch does seem to work.  For
example the following...

| 2:30 | 2 | 75 |
#+TBLFM: $3=$1/$2

It may make sense to also include functionality for converting the
result back into a time string, e.g.

#+begin_src emacs-lisp
  (defun org-time-seconds-to-string (secs)
    "Convert a number of seconds to a time string."
    (cond ((>= secs 3600) (format-seconds "%h:%.2m:%.2s" secs))
          ((>= secs 60) (format-seconds "%m:%.2s" secs))
          (t (format-seconds "%s" secs))))
#+end_src

| 2:30 | 2 | 1:15 |
#+TBLFM: $3='(org-time-seconds-to-string (/ (string-to-number $1) (string-to-number $2)))

While the above is cumbersome, there may be a simpler syntax or
convention -- e.g., whenever one of the inputs is a time string then the
results are displayed as a time string.  Not sure what the best option
is here, but thought this patch may spur some good suggestions.

Best -- Eric