Calculating Leap Year

I set up a table with approximately 200 years in it. Then using the formula from Wikipedia, I calculated whether it was a leap year or not.

If (
   (Year Modulo   4 Is     0) And
   (Year Modulo 100 Is Not 0)
 )
Or   (Year Modulo 400 Is     0)
Then Leap
Else No_Leap

To double-check, I set up the year with February, and asked what the last day of the month was. The subquery did all the work; the parent query asked for a count of distinct combinations.

Column Leap_or_No Heading 'Leap|or No'
Column Day        Heading 'Feb|Last|Day' Format A4

Select Leap_or_No,
     To_Char(FebDay,'dd') Day,
     Count(*)
From (
      Select Year,
             -------------------------------------------
                      Case When (Mod(Year,   4)= 0
                            And  Mod(Year, 100)<>0
                                )
                             Or  Mod(Year, 400)= 0
                           Then 'Leap'
                           Else 'No Leap'
                       End
                       As
             Leap_or_No,
             --------------------------------------------
                       Last_Day(To_Date('01-Feb-'||Year))
                       As
             FebDay
             ---------------------------------------------
        From Year
      )
Group By Leap_or_No,
         To_Char(FebDay,'dd') ;

See Oracle documentation for further detail: Mod