...
Notes
A = high byte, C = low byte. If result stored at (DE) then (DE) = low byte, (DE+2) = high byte (Z80 convention).
Related calls
GN_Gtm, convert an ASCII string to a time in internal format
GN_Msc, miscellaeneous time operations
GN_Pmt, put (set) machine time
GN_Ptm, write internal time as ASCII string
GN_Sdo, send date and time to standard output
OS_Dly, delay a given period