machuoka

10 INPUT"YEAR:",Y:INPUT"MONTH:",M ' IchigoJam: @machuoka
20 IF M=2 THEN L=28+((Y%4=0)*(((Y%100<>0)+(Y%400=0))>0)):GOTO 40
30 L=31-((M=4)+(M=6)+(M=9)+(M=11))
40 IF M<3 THEN Y=Y-1:M=M+12
50 S=(Y+Y/4-Y/100+Y/400+(M*13+8)/5+1)%7
60 I=S:D=1
70 IF I=0 GOTO 90
80 PRINT"   ";:I=I-1:GOTO 70
90 IF D<10 THEN PRINT" ";
100 PRINT D;" ";:IF D=L THEN PRINT:END

machuoka

10 INPUT"YEAR:",Y:INPUT"MONTH:",M
20 IF M=2 THEN L=28+((Y%4=0)*(((Y%100<>0)+(Y%400=0))>0)):GOTO 40
30 L=31-((M=4)+(M=6)+(M=9)+(M=11))
40 IF M<3 THEN Y=Y-1:M=M+12
50 S=(Y+Y/4-Y/100+Y/400+(M*13+8)/5+1)%7
60 IF M>12 THEN Y=Y+1:M=M-12
70 I=S:D=1
80 PRINT:PRINT"     ";Y;" / ";M
90 PRINT:PRINT"S  M  Tu W  Th F  S"
100 IF I=0 GOTO 120