fabiochelly
18th February 2004 10:59 UTC

Here are 2 useful date functions
I created 2 date functions: IsLeapYear and DaysInMonth:

To use it:
Push "year"
Call IsLeapYear
Pop $0 ;returns 0 or 1

Push "month"
Push "year"
Call DaysInMonth
Pop $0 ; returns 28, 29, 30 or 31

Function IsLeapYear

  Pop $0
  IntOp $1 $0 % 4
  IntCmp $1 0 test2 ;si divisible par 4, on passe au test 2 (début de siècle)
  Goto ko ;sinon, retourne FAUX
  test2:
    IntOp $1 $0 % 100
    IntCmp $1 0 test3
    Goto ok
  test3:
    ;l'année est un siècle rond
    ;on vérifie si ce siècle est impair
    IntOp $1 $0 % 200
    IntCmp $1 0 ok
    Goto ko
  ok:
    Push 1
    Goto end
  ko:
    Push 0
  end:
FunctionEnd

Function DaysInMonth
  Pop $0 ;annee
  Pop $1 ;mois

  IntCmp $1 1 m31
  IntCmp $1 2 m28
  IntCmp $1 3 m31
  IntCmp $1 4 m30
  IntCmp $1 5 m31
  IntCmp $1 6 m30
  IntCmp $1 7 m31
  IntCmp $1 8 m31
  IntCmp $1 9 m30
  IntCmp $1 10 m31
  IntCmp $1 11 m30
  IntCmp $1 12 m31

  m31:
    Push 31
    Goto end
  m30:
    Push 30
    Goto end
  m28:
    Push $0
    Call IsLeapYear
    Pop $0
    IntCmp $0 1 m29
      Push 28
      Goto end
    m29:
     Push 29
  end:
FunctionEnd

deguix
18th February 2004 11:04 UTC

Maybe you based "Bissext" year from one of my functions, the correct name is "Leap" year.

And second, you can know if a year is a leap year using the simple calculation:

Year % 4

If the rest is 0, it is a leap year.

I should fix those two in my function but I didn't have time to do that.

fabiochelly
18th February 2004 11:08 UTC

Leap and not Bissext : corrected

No: Year / 4 is not enough : years 1700, 1900, 2100, 2300 (each 200 years) are not leap.

Effectively, I called it Bissext because I first tried to use your Seconds2Date function which doesn't work for me (see my other thread of this day)

deguix
18th February 2004 11:21 UTC

Yes, all of them are leap years. Why did Atlanta celebrated the 100th Olimpiada in 1996?

Joost Verburg
18th February 2004 14:01 UTC

Fabiochelly is correct.

Every year divisible by 4 is a leap year.

However, every year divisible by 100 is not a leap year.
However, every year divisible by 400 is a leap year after all.

So, 1700, 1800, 1900, 2100, and 2200 are not leap years. But 1600, 2000, and 2400 are leap years.

fabiochelly
18th February 2004 14:02 UTC

see http://www.galactic-guide.com/articles/6R87.html

The explanation here:
http://www.multicians.org/jhs-clock.html

or here:
http://www.timeanddate.com/date/leapyear.html

In fact:
1. Every year divisible by 4 is a leap year.
2. But every year divisible by 100 is NOT a leap year
3. Unless the year is also divisible by 400, then it is still a leap year.

deguix
18th February 2004 14:27 UTC

Bah, I have to fix my function anyways...