Use this just like the Unix program diff. It's smart enough to ignore
differences in time triples (those numbers printed at the end of each
event). It's not by any means perfect, but it works quite well when
the files differ only in time triples.
Usage:
nqthmdiff file1 file2
To compile this, run your Ansii Standard C compiler (i.e., probably
not the old-style compiler cc that comes with your Unix-based system)
on the source file, e.g.
gcc nqthmdiff.c -o nqthmdiff
See also nqthmdiff.el, in the emacs subdirectory.