Answer and Explanation:
The year which is directly divided by 400 will be a leap year and by 4 for example 2000 1600 are leap year because they are directly divided by 400 and the year 1700 and 1800 although they are divided by 4 but not by 400 so they are not leap year,This is the reason even 1800 is divided by 4 but not a leap year