# An explanation for having and not having leap years.

Hello netizens! happy new year and other relevant greetings. Here is a simple explanation for having leap years. Basically, my take on something which has been talked about and explained many times already.

So, as you all know, The Earth revolves around the sun and rotates along its own axis (unless you are a flat-earther or did not go to school) and one full revolution makes one year.

Here is the explanation

1 year = 365.242375 days
(1 year is around 365.242375 days)

~= 365.25 days

therefore 1 day is added every 4 years (because 4 * 0.25 = 1)

So,
in 100 years, 25 days are added, so, one day is skipped every 100th year.
BUT
The 400th year has the extra day

Didn’t get it? Go on, keep reading.

1 year is approximately 365.242375 days.
For convenience, we consider it to be 365.25 days. This 0.25 part is skipped for 3 years and an extra day is added to the fourth year to compensate the said skipping of days.
Following this, in 100 years, 25 days are added. 100 years are of 36524.2375 days. By rounding it off, they are 36525 days. In this manner, we are getting an extra day every 100th year. So, that extra day is skipped the 100th year to have only 36524 days.
In 4 sets of 100 years, or 400 years, an extra day is needed to compensate for the four sets of the 0.2375 day(s) left every 100 years.

Hence, Every 4th year is a leap year.
Every 100th year is NOT a leap year.
BUT
Every 400th year IS a leap year.

All this extra effort is due to the Gregorian calendar and limitations of human time-keeping ability.