MATHEMATICS

I discovered this goodie, which could be useful to many of us, amongst the FB archives. It appears to be exactly what I'm looking for, but I can't find the key to extracting the day.
Clues, anyone?

'==========================
' dayofweek - Calculate day of the week index
' At entry dd=date, mm=month, yy=year in format nnnn e.g. 1991
' this date should first be validated
' At exit z=index to day of the week (1=Sunday, 7=Saturday)
' routine valid for dates 1-1-1583 through 12-31-9999

'Subj: Re:Day of Week Clarification
'Date: 96-03-15 18:18:44 EST
'From: WatsonR

'==========================
LOCAL FN DayOfWeek(mm,dd,yy)
  t!=1/mm
  k1=0.6+t! : l1=yy-k1
  t!=12*k1
  o1!=mm+t! : p1#=l1/100
  z1=INT(p1#/4) : z2=INT(p1#) : z3=INT((5*l1)/4)
  z4=INT(13*(o1!+1)/5) : z=z4+z3-z2+z1+dd
  z=z-(7*INT(z/7))
END FN=z
'----------

dayNum% = FN DayOfWeek(3,18,1999) 'for March 18, 1999

SELECT CASE dayNum%
	CASE 1: day$ = "Sunday"
	'
	'
	CASE 7: day$ = "Saturday"
END SELECT

Here's what I use and it still works. The Year is in 4 digits (1999) not PC format.

LOCAL FN Date2Julian&(Day, Month, Year)
   '
   LONG IF Month<3
	 Month=Month+12
	 DEC(Year)
   END IF
   INC(Month)
   '
   Julian&=(365.25*Year)+(30.6001*Month)+Day+1720982
   '
END FN = Julian&
'
LOCAL FN DayOfWeek$(Julian&)
   SELECT CASE Julian& MOD 7
	 CASE 0
	   DayOfWeek$ = "Monday"
	 CASE 1
	   DayOfWeek$ = "Tuesday"
	 CASE 2
	   DayOfWeek$ = "Wednesday"
	 CASE 3
	   DayOfWeek$ = "Thursday"
	 CASE 4
	   DayOfWeek$ = "Friday"
	 CASE 5
	   DayOfWeek$ = "Saturday"
	 CASE 6
	   DayOfWeek$ = "Sunday"
   END SELECT
END FN = DayOfWeek$
'
LOCAL FN BuildDate$(M,D,Y):             ' builds date string from MONTH,DAY,YEAR
   DateStr$="..-..-....":               ' cancel out the old one first
   MID$(DateStr$,1,2)=RIGHT$(STR$(M),2):' extract the month first
   MID$(DateStr$,4,2)=RIGHT$(STR$(D),2):' extract the day next
   MID$(DateStr$,7,4)=RIGHT$(STR$(Y),4):' extract the year last
   IF MID$(DateStr$,1,1)=" " THEN MID$(DateStr$,1,1)="0":' add in a zero
   IF MID$(DateStr$,4,1)=" " THEN MID$(DateStr$,4,1)="0":' add in second zero
END FN = DateStr$
'
LOCAL FN Julian2Date$(Julian&)
   U&=Julian&+68569
   V&=INT(4*U&)/146097
   U&=-INT(((146097*V&)+3)/4)+U&
   Y&=INT(4000*(U&+1))/1461001
   U&=-INT((1461*Y&)/4)+31+U&
   M&=INT(80*U&)/2447
   D&=-INT((2447*M&)/80)+U&
   U&=INT(M&/11)
   M&=-12*U&+2+M&
   Y&=100*(V&-49)+Y&+U&
   Year=Y&:Month=M&:Day=D&
   DateStr$= FN BuildDate$(Month,Day,Year)
END FN=DateStr$

Heres a bright idea, lets use the toolbox to do it all for us, its much = less code...

DIM myDateRec.DateTimeRecSize

myDateRec.Day%   = 17
myDateRec.Month% = 10
myDateRec.Year%  = 1999

myDateAsSeconds& = FN DATE2SECS(@myDateRec)
CALL SECS2DATE(myDateAsSeconds&,@myDateRec)
PRINT "Day Of Week as Number: ";myDateRec.DayOfWeek%