It's Leap Year!

I'm sure everyone know this year is a 'leap year' because this February has 29 days... I won't forget blogging on this '4 years once' date. Who knows if this blog still exist after 4 years.

It's common sense that leap year can evenly divided by 4. But in fact, the year that divisible by 100 is not a leap year unless it also divisible by 400. Why?

Current calendar (Gregorian calendar) is a solar calendar which dates indicate the position of the earth on its revolution around the sun. One normal year contains 365 days, but 1 circulation of earth is 365 1/4 days. So a leap year occured every 4 years to cover up the missing day. However, 1 circulation is assumed as 365.2425 days in 4 decimal places. We actually advanced about 43 minutes every leap year... To correct this, every 25th leap year need to be skipped to 'slow down' the calendar untill the 100th leap year.

{ 0.72 hours x 100 = 72 hours (3 days skipped on 25th,50th, and 75th leap year) }

Until that was from 'Annual level' to 'century level', now I'm gonna move to 'millenium level'. LoL, what the heck! Well, the more accurate circulation period is actually 365.24219.... So, Sir John Herschel suggested make 4000 A.D. not a leap year to reduce the average year period to 365.24225 which is closer to perfect accuracy. Will earth survive till then? I doubt...

End of my bullshits