The year devisible by 400 are leap year [like 1600,2000,2400]
The year which are devisible by 4 but not by 100 are leap year[like 1996, 2004]
but the year which are not devisible by 4 or (devisible by 100 and not devisible by 400 are not leap year [like 2003 and 2100 is not a leap year]