Challenge: Compute the number of Tuesdays since a given date

[Neo]

(1)
' 1-1-1900 was a Sunday (backtracked)
NO, IT WAS A MONDAY.

This is caused by my explaination at comment (2).

(2) IF INT(NowYear / 4) * 4
THIS IS NOT A VERY GOOD WAY TO CHECK FOR LEAP YEAR. FOR EXAMPLE, THIS CODE WOULD CONSIDER 1900 AS A LEAP YEAR, WHICH IT WAS NOT. SEE THË "ISLEAPYEAR" FUNCTION AND COMMENTS AT THE END OF MY POSTED SOLUTION ABOVE.
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Hrmm, I thought every year, multiplier of 4 was a leap year. (read your IsLeapYear)... hrmmm... ok right. So 1900 was not... that means 1-1-1900 wasn't a Sunday but a Monday indeed (counted 1 day extra: 29-2-1900). To solve this problem, do this:

Replace:

Code:

IF INT(NowYear / 4) * 4 = NowYear THEN DaysPerMonth(2) = 29 ELSE DaysPerMonth(2) = 28

by:

Code:

IF (NowYear MOD 4 = 0 AND NowYear MOD 100 <> 0) OR (NowYear MOD 400 = 0) THEN DaysPerMonth(2) = 29 ELSE DaysPerMonth(2) = 28

(didn't even know this but I learnt from your function )