How do you find Leapyear in VBA?

Question

What is a good implementation of a IsLeapYear function in VBA?

Edit: I ran the if-then and the DateSerial implementation with iterations wrapped in a timer, and the DateSerial was quicker on the average by 1-2 ms (5 runs of 300 iterations, with 1 average cell worksheet formula also working).

Answer 1

Public Function isLeapYear(Yr As Integer) As Boolean  

    ' returns FALSE if not Leap Year, TRUE if Leap Year  

    isLeapYear = (Month(DateSerial(Yr, 2, 29)) = 2)  

End Function

I originally got this function from Chip Pearson's great Excel site.

Pearson's site

Answer 2

public function isLeapYear (yr as integer) as boolean
    isLeapYear   = false
    if (mod(yr,400)) = 0 then isLeapYear  = true
    elseif (mod(yr,100)) = 0 then isLeapYear  = false
    elseif (mod(yr,4)) = 0 then isLeapYear  = true
end function

Wikipedia for more... http://en.wikipedia.org/wiki/Leap_year

Answer 3

If efficiency is a consideration and the expected year is random, then it might be slightly better to do the most frequent case first:

public function isLeapYear (yr as integer) as boolean
    if (mod(yr,4)) <> 0 then isLeapYear  = false
    elseif (mod(yr,400)) = 0 then isLeapYear  = true
    elseif (mod(yr,100)) = 0 then isLeapYear  = false
    else isLeapYear = true
end function

Answer 4

I found this funny one on CodeToad :

Public Function IsLeapYear(Year As Varient) As Boolean
IsLeapYear = IsDate("29-Feb-" & Year)
End Function

Altough i'm pretty sure that the use of IsDate in a function if probably slower than a couple if, elseif.