Calendar | MSX-BASIC https://msxjpn.jimdofree.com/%E3%83%97%E3%83%AD%E3%82%B0%E3%83%A9%E3%83%A0/%E3%82%AB%E3%83%AC%E3%83%B3%E3%83%80%E3%83%BC/

calendar.bas

' Calendar | MSX-BASIC
' Copyright (c) 2025 BALLOON | FU-SEN
' The MIT License (MIT) - https://mit.balloon.net.eu.org/#2025
100 DIM D(12)
110 INPUT "Year ";Y
120 INPUT "Month";M
130 FOR I=1 TO 12
140 READ D(I)
150 NEXT I
160 IF Y MOD 4=0 AND (Y MOD 100<>0 OR Y MOD 400=0) THEN D(2)=D(2)+1
170 IF M<3 THEN Y=Y-1:M=M+12
180 I=INT(Y+INT(Y/4)-INT(Y/100)+INT(Y/400)+INT((13*M+8)/5)+1) MOD 7
190 IF M>12 THEN M=M-12
200 PRINT "SunMonTueWedThuFriSat"
210 PRINT STRING$(3*I,32);
220 FOR J=1 TO D(M)
230 PRINT USING "###";J;
240 I=I+1
250 IF I=7 THEN PRINT:I=0
260 NEXT J
270 DATA 31,28,31,30,31,30
280 DATA 31,31,30,31,30,31