It’s almost Leap Day yet, and I came across a fantastic article about the WHY of Leap Day. Here’s the link: Fixing the Fault in our Stars, by James Hetrick. Read on for a synopsis.
Blame it on the Stars?
The measure of a year is the time it takes for the earth to return to the same place in relation to the stars that are fixed or constant.
At the end of the 365 days that measure our normal year, there are still almost six hours needed to reach the same place in relation to the stars. Humans have known about this for a long time. Julius Caesar sought to fix the problem with the Julian calendar, adding an extra day every four years. But that overcompensated too much.
So in the late sixteenth century, Christopher Clavius, astronomer for Pope Gregory, fine-tuned the calculations and developed the Gregorian Calendar. (I’m sure Caesar didn’t create the Julian calendar either–the guy in charge always gets the glory.)
The fine-tuning? Quoting from Hetrick’s article:
- Every year divisible by 4: Add February 29
- Every century (1800, 1900, 2000, 2100): do not add February 29
- Every century divisible by 400, add February 29 [so next in 2400]
Mother Earth Misbehaving
Planetary occurrences can mess things up by making time slip. Here’s an interesting tidbit:
The 8.9 magnitude earthquake that triggered the Japanese Tsunami on March 11, 2011…shifted the planet’s mass distribution enough to decrease the length of a day by 1.8 microseconds. This will add up to about a second after 1500 years.
Who measures the time slips? That would be the International Earth Rotation and Reference Systems Service. I’m so glad someone is keeping track of this for us!
If you’d like to read more, follow the links above, and/or check out my post from the 2016 Leap Day.
And don’t forget my Leap Day novella! It’s a short, sweet read. You won’t need more than a couple of those extra 24 hours to read it!
Image credits: GetStencil.com, BookBrush