[comp.sys.atari.st] Calendar Formula needed

harryk@bucsf.bu.edu (Harry Karayiannis) (03/11/90)

  Hi world...

	perhaps this has been asked before but I really need to know if there
     	is a formula which returns the 1st day of a given month in a given
        year!
	(i.e.
	  -Input:  YEAR  = 1990
	  	   MONTH = 1 (January)

	  -Output: DAY = ??formula?? = 2 (Monday)
	)


  I think that Dave Shumacher (the author of DLibs) had found such a formula
  and he had talked about it in the net...but unfortunately i missed that dis-
  cusion!

  So if anyone remembers it (or knows a different one) PLEASE send me E-mail


  Thank You!!

PS: If your mail to the above address bounces try: cscrzcc@buacca.bu.edu

eer36024@uxa.cso.uiuc.edu (03/13/90)

This may be more than what you need.  This converts a year, month, and day
to a "Julian Day" number.  A Julian Day number MOD 7 = 0=Monday to 6=Sunday.

ALL '/'s = DIV, i.e.  A/B = A DIV B = TRUNC(A/B)

JD = 367*Y - 7*(Y+(M+9)/12)/4 - 3*((Y+(M-9)/7)/100+1)/4 + 275*M/9+D+1721029