Birthday — Calculates birthdays

This procedure finds out on which day of the week people were born.

    PROC Birthday:
          LOCAL day&,month&,year&,DayInWk%
          DO
                dINIT
                dTEXT "","Enter your date of birth",2
                dTEXT "","Use numbers, eg 23 12 1963",$202
                dLONG day&,"Day",1,31
                dLONG month&,"Month",1,12
                dLONG year&,"Year",1900,2155
                IF DIALOG=0
                      BREAK
                ENDIF
                DayInWk%=DOW(day&,month&,year&)
                CLS :PRINT DAYNAME$(DayInWk%),day&,month&,year&
                dINIT "Again?"
                dBUTTONS "No",%N,"Yes",%Y
          UNTIL DIALOG<>%y
    ENDP

The DOW function works out what day of the week, from 1 to 7, a date is. The DAYNAME$ function then converts this to MON, TUE and so on. MON is 1 and SUN is 7.