Good morning, John! Happy new year!

(party blower)

It's a time of reflecting on the year that has past and hoping for a good one to come but also, as I am incapable of not doing, asking why. Why is it this way? Why January 1st? And if it's gonna be January 1st, why isn't January 1st on the solstice? Well, I will give you a hint: this monumental modern institution of our calendar and the way that it works and begins has to do with three people who you have never heard of.

The earth travels around the sun in a circle, and there is no beginning or end to a circle. You wanna have a beginning of the year- I get that. And basically, we have traditionally just picked one. And different cultures have picked different dates for different reasons, and they turn out to be really interesting and complicated reasons. Complicated enough that I can really only talk about one, and I'm gonna pick the one I'm most familiar with.

So let's go back to 46 B.C. Julius Caesar has just become the first emperor of Rome, and the calendar is a mess. It's based on this calendar that's hundreds of years old, that started out only having ten months, so December being the last month and March being the first month. And it's a lunar calendar. Every month begins with a new moon, and there's a full moon in the middle, and it ends again with a new moon. But since the lunar calendar and solar calendar don't line up, they had to have some way of getting realigned each year. And that system (and I'm not kidding here) was 51 days of unaffiliated buffer time that occurred between December and March that just weren't inside of any month. 

But in the 700s BC one of the original kings of Rome, Numa Pompilius, one of the guys you haven't heard of, decided this system just wasn't gonna cut it. So he added two new months to the beginning of the year. You've heard of them- January and February. This resulted in a number of months having Latin prefixes that no longer aligned with their position in the year, which is an immense source of frustration for me. But that is when January 1st became the first day of the new year in Rome. Weirdly, though, January 1st kept falling on what we would consider different days. Because the behavior of the moon and the behavior of the sun kept not having anything to do with each other, so in order to keep having the summer months happen in the summer, they had to keep messing with the number of days in each month, and then they would have to add extra months sometimes. It was super confusing. 

Julius Caesar, like any good dictator, wanted to establish some dang order. He consulted an Alexandrian astronomer named Sosigenes, who suggested that they scrap the lunar calendar completely in favor of a solar calendar, like the ones that the recently conquered Egyptians had. Sosigenes had calculated that the solar year was 365.25 days, so he suggested a year 365 days long with an added extra day thrown in every four years during the shortest month, February. Probably sounds familiar to you. Caesar now had the opportunity to establish when January 1st would appear on the solar calendar, and he could have picked the solstice. But as one last final shout out to the lunar calendar, he put it on the new moon that was closest to the solstice, which just happened to be about nine days later. So yes, the date of a new moon in 45 BC decided when January 1st would appear on the solar calendar.

Kinda! Because the solar year is actually slightly shorter than 365.25 days, the drift began again. By the Middle Ages, people were confused enough that they were basically celebrating the new year whenever they felt like it until 1582 when Pope Gregory the 13th consulted an Italian astronomer. Aloysius Lilius, the last guy you haven't heard of, proposed to Pope Gregory a solution for these drifting days- slight modification of the Leap Year schedule having only 97 leap years every 400 years instead of 100 every 400 years. Pope Gregory then instituted and mandated this new calendar, which we call the Gregorian calendar, and we still basically use today.

So Numa Pompilius, Sosigenes, Aloysius Lilius, thank you very much [for] your contributions to our world today. I'm sorry everybody's forgotten about you. But here we are, John, celebrating those people, entering the year 2016, our 10th year of vlogging on YouTube. Wow!

I was super interested to see people's comments on your last video, but I felt like that was extraordinarily unscientific, and we weren't getting good data, so I set up an actual survey that people can take. There's a link in the description if you want to answer some questions about what we should do in the next year on Vlogbrothers. John, thanks for being a great brother. Thanks for another great year, and I'll see you on Tuesday.