10 REM > Days4
   20 REM calculates day of week
   30 MODE 27:REM use mode 12 for standard resolution monitor
   40 ON ERROR REPORT:PRINT " at line ";ERL:END
   50 COLOUR 128+4
   60 DIM monnum%(12),day$(6)
   70 FOR m%=1 TO 12:READ monnum%(m%):NEXT
   80 FOR d%=0 TO 6:READ day$(d%):NEXT
   90 ON ERROR PROCerror
  100 REPEAT
  110   CLS
  120   INPUT TAB(15,10) "Please enter the day of the month "date%
  130   INPUT TAB(15,11) "Now enter month number (1-12) "mon%
  140   INPUT TAB(15,12) "Now enter the year "year%
  150   IF year%<40 year%+=100
  160   IF year%<140 year%+=1900
  170   IF year%<1900 OR year%>2099 THEN ERROR 1<<30,"Sorry, this program only 
works with years 1900 to 2099"
  180   year%-=1900
  190   leaps%=year% DIV 4
  200   IF (year% MOD 4)=0 AND mon%<3 AND year%>0 THEN leaps%-=1
  210   total%=year%+leaps%+monnum%(mon%)+date%
  220   total%=total% MOD 7
  230   COLOUR 3
  240   PRINT TAB(15,14) "That day was a ";:COLOUR 7:PRINT day$(total%)
  250   PRINT TAB(15,16) "Do you want another go (y/n)"
  260   char$=GET$
  270 UNTIL char$<>"Y" AND char$<>"y"
  280 END
  290 DATA 0,3,3,6,1,4,6,2,5,0,3,5
  300 DATA Sunday,Monday,Tuesday,Wednesday,Thursday,Friday,Saturday
  310 :
  320 DEFPROCerror
  330 CASE ERR OF
  340   WHEN 1<<30:PRINT TAB(10,14)REPORT$':PRINT TAB(10,16) "Press any key to 
continue";:REPEAT UNTIL GET
  350   OTHERWISE
  360   REPORT:PRINT " at line ";ERL:END
  370 ENDCASE
  380 ENDPROC
  390 :