REM
REM Demo implementing Zeller's Congruence
REM http://en.wikipedia.org/wiki/Zeller_congruence
REM
REM March 2009 - PvE.
REM Revised december 2009.
REM Revised may 2010.

INPUT "Enter day of the month (1-31): ", q
IF q > 31 OR q < 1 THEN
    PRINT "Day must be within 1-31!"
    END
ENDIF

INPUT "Enter month (1-12): ", m
IF m > 12 OR m < 1 THEN
    PRINT "Month must be within 1-12!"
    END
ENDIF

INPUT "Enter year: ", year$

REM the LET statement is optional 
LET J = VAL(LEFT$(year$, 2))
LET K = VAL(MID$(year$, 3, 2))

IF m EQ 1 OR m EQ 2 THEN
    INCR m, 12
    DECR K
ENDIF

REM Here the LET is omitted
h = (q + ((m+1)*26)/10 + K + (K/4) + (J/4) + 5*J)

day = MOD(h, 7)

SELECT day
    CASE 0
	PRINT "That is a Saturday."
    CASE 1
	PRINT "That is a Sunday."
    CASE 2
	PRINT "That is a Monday."
    CASE 3
	PRINT "That is a Tuesday."
    CASE 4
	PRINT "That is a Wednesday."
    CASE 5
	PRINT "That is a Thursday."
    CASE 6
	PRINT "That is a Friday."
END SELECT