Why Do We Have Leap Years?

So it's February 29th and we have 366 days this year instead of 365- what's the deal with Leap Years? ---------- Support SciShow by becoming a patron on Patreon:   / scishow   ---------- Dooblydoo thanks go to the following Patreon supporters -- we couldn't make SciShow without them! Shout out to Justin Ove, Fatima Iqbal, Linnea Boyev, Kathy & Tim Philip, Kevin Bealer, Justin Lentz, Chris Peters, and Philippe von Bergen. ---------- Like SciShow? Want to help support us, and also get things to put on your walls, cover your torso and hold your liquids? Check out our awesome products over at DFTBA Records: http://dftba.com/scishow ---------- Looking for SciShow elsewhere on the internet? Facebook:   / scishow   Twitter:   / scishow   Tumblr:   / scishow   Instagram:   / thescishow   ---------- Hosted by: Hank Green Sources: http://scienceworld.wolfram.com/astro... http://www.britannica.com/science/Bab... http://scienceworld.wolfram.com/astro... https://books.google.com/books?id=5O7... http://www.wolframalpha.com/input/?i=... http://www.wolframalpha.com/input/?i=... http://penelope.uchicago.edu/~grout/e... http://www.livius.org/articles/concep... http://www.gutenberg.org/cache/epub/1... http://www.newworldencyclopedia.org/e... http://www.wolframalpha.com/input/?i=... http://www.biblicalcatholic.com/apolo... http://www.britannica.com/topic/pontifex http://www.wolframalpha.com/input/?i=... http://www.wolframalpha.com/input/?i=... http://adsabs.harvard.edu/abs/1992JBA... http://www.wolframalpha.com/input/?i=...