INT 1A - TIME - GET REAL-TIME CLOCK DATE (AT,XT286,PS)
        AH = 04h
Return: CF clear if successful
            CH = century (BCD)
            CL = year (BCD)
            DH = month (BCD)
            DL = day (BCD)
        CF set on error
SeeAlso: AH=05h,INT 21/AH=2Ah