PRINT "Jahr - year, Monat - month, Tag - day"
INPUT jjjj, m, t


REM conway - algorithm
j = jjjj - INT(jjjj / 100) * 100 : rem remove century

j = j MOD 19
IF j > 9 THEN
   j = j - 19   
END IF

j = (j * 11) MOD 30
  
j = j + t + m
IF m < 3 THEN
   j = j + 2
END IF

j = j - 4           : rem 19.. century -4
IF jjjj > 1999 THEN
   j = j - 4.3      : rem 20.. century -8,3
END IF

j = (j + 30) MOD 30 : REM day 0-29 Age of moon 0=new moon 14/15=full moon

IF j = 14 or j = 15 THEN
   PRINT "Vollmond - full moon"
ELSEIF j = 0 THEN
   PRINT "Neumond - new moon"
ELSE
   IF j < 14 THEN
      PRINT "zunehmend - noch ca."; 14 - j; " Tag(e) bis Vollmond"
   ELSE
      PRINT "abnehmend - noch ca."; 30 - j; " Tag(e) bis Neumond"
   END IF
END IF

REM calculation (+/- 1-2 days) of lunar phase
REM MS - QBasic
REM Juergen Galupki http://galupki.de 1999-04-24
REM source:
REM John Horton Conway (the Princeton mathematician who is responsible for
REM "the Game of Life") wrote a book with Guy and Berlekamp, _Winning
REM Ways_, that describes in Volume 2 a number of useful calendrical
REM rules.  One of these is an easy "in your head" algorithm for
REM calculating the phase of the Moon, good to a day or better depending
REM on whether you use his refinements or not.
REM FAQ Astronomy - Subject: C.11  How do I calculate the phase of the moon?
REM Author: Bill Jefferys <bill@clyde.as.utexas.edu>