*HMS* stands for Hours-Minutes-Seconds; when used as an angular
argument, the interpretation is Degrees-Minutes-Seconds. All functions
that operate on angles accept HMS forms. These are interpreted as
degrees regardless of the current angular mode. It is also possible to
use HMS as the angular mode so that calculated angles are expressed in
degrees, minutes, and seconds.

The default format for HMS values is
‘` hours@ mins' secs"`’. During entry, the letters
‘

HMS forms can be added and subtracted. When they are added to numbers, the numbers are interpreted according to the current angular mode. HMS forms can also be multiplied and divided by real numbers. Dividing two HMS forms produces a real-valued ratio of the two angles.

Just for kicks, `M-x calc-time` pushes the current time of day on
the stack as an HMS form.