69h TM$DAYV calculate day of the week
Input X register - Address of time buffer.
Output B register - numeric value of day.
X register - address of 3 byte day name.
Description Calculates the day of the week for a given date between 1 JAN 1900 and 31 DEC 1999 (CM/XP) or 31 DEC 2155 (LZ). X must point to the time buffer containing the particular date in the standard format (three bytes:year 0-99/0-255, month 0-11, day 0-30).

The numeric value of the day (0 to 6) is returned in the B register (0 represents MONDAY, 1 TUESDAY, etc) and X will point to the corresponding 3 byte day name in ascii (MON,TUE,WED,THU,FRI,SAT or SUN).

Example The following routine will calculate and print the day for 2 JAN 1963:
        LDX     #BUFFER         ;POINT TO TIME BUFFER
        LDD     #3F00h          ;YEAR 1963, MONTH JANUARY
        STD     0,X
        LDAA    #01h            ;DATE 2ND
        STAA    2,X
        OS      TM$DAYV         ;CALCULATE DAY
        LDAA    3
        PSHA                    ;DAY NAME LENGTH
        PSHX                    ;ADDRESS OF DAY STRING
        OS      UT$DISP
        DB      0Ch             ;CLEAR DISPLAY
        DB      "%b"            ;PRINT DAY
        DB      0
Errors - none -