Moonphase Astrology

   10 REM MOONPHASE ASTROLOGY
   20 GO TO 1000
  100 REM input date
  110 CLS 
  130 PRINT "DETERNINATION OF MOONPHASE"
  135 PRINT 
  140 INPUT "DAY (dd): ";dd: PRINT "Day : ";dd
  150 INPUT "Month (mm): ";m: PRINT "Month: ";m
  160 INPUT "Year (yyyy): ";y: PRINT "Year: ";y
  170 IF m<3 THEN LET m=m+12: LET y=y-1
  180 RETURN 
  200 REM calculation
  210 LET t=INT (365.25*y)+INT (30.6*(m+1))+dd-694038
  220 LET t=t/36525
  230 LET la=350.737486+1236*t*360
  240 LET la=la+307*t+6*t/60
  250 LET la=la+51.18*t/3600-5.17*t*t/3600
  260 LET la=la-INT (la/360)*360
  270 LET la=INT (la+.5)
  280 RETURN 
  300 REM display result
  310 PRINT : PRINT 
  320 PRINT "Moonphase=";la;" degrees"
  330 PRINT : PRINT "Press any key"
  340 IF INKEY$="" THEN GO TO 340
  350 RETURN 
 1000 REM main program
 1010 GO SUB 100: REM input date
 1020 GO SUB 200: REM calculation
 1030 GO SUB 300: REM display result
 1040 GO TO 1010
 9997 STOP 
 9998 SAVE "MOONPHASE" LINE 1