The function returns 365 for a normal year and 366 for a leap year. The calculation for leap year is based on:
(year) %4 == 0 && ((year) %100 != 0 || (year) %400 == 0)
The formula is defined in the macro __isleap(year) also found in <time.h>.
This function occurs in SunOS 4.x.
This is a compatibility function only. Dont use it in new programs. The SCO version of this function had a year-2000 problem.