A string of the form hh:mm:ss that is the time left after subtracting.
|MinuendVariable||What gets subtracted from.|
|Subtrahend||How much to subtract.|
Note that the strings represent quantities of time, how long. The strings do not represent time points, times during the day.
For information regarding exceptions / errors, see here
Here we subtract 30 minutes from 90 minutes and get back an hour.
% DiffHhmmss 01:30:00 00:30:00