 Greetings and welcome to the Introduction to Astronomy. In this week's Astronomy of Other Cultures, we are going to continue looking at Chinese astronomy and specifically focus on the calendar that was used. So let's go ahead and get started with that. And what we see is that the Chinese use what is called a Lunar Solar Calendar. And that means it's based on both the moon and the sun. So we use two things are used here and it dates back 3500 years or even more. So what it has done is it's based on measurements of the sun and the lunar phase cycle. So things that were very easy to see, you could watch the moon go through its phases. And we see here early recordings of some of that here marked on in this very early sample. Now things were divided up a little bit differently than what we do and we've seen that with other calendars that we've looked at, but a typical year had 354 days. Why? Why such an odd number of days? Well that is 29 and a half, which is the cycle of phases of the moon, times 12. So 12 months, a month was exactly 29 and a half days. There were 12 of those in the year and if you multiply those two together you get 354. Now that's the number of days there. Now of course we know that the earth takes 365 days to go around the sun. So you know that that's going to get off very quickly. However they did use leap years just as we do here, but while our leap year has only one extra day, their leap year had an entire extra month and was 384 days long. So you'd have, your years would balance about every three years out. You'd have two short years and then you'd have one much longer year with an extra month with 13 months in it to bring everything back into a cycle there. Now the Chinese also had what was called a sexagenary cycle that was used. Now you may be familiar with this with the Chinese zodiac and it is, you tend to see that as 12 and the 12 different animals representing the different years, but it's actually a 60 year cycle based on what they call 10 heavenly stems based on 10 days of the week and the 12 earthly branches which was the 12 year cycle of Jupiter. Now you might think with 10 years and 10 day here and 12 years you'd get 120, but only half of these are actually used, giving us the 60 year complete cycle of the Chinese zodiac. So while we talk about the year, whether it's the year of the dog or the year of whatever other animal happens to be, there are also more details involved in that that were used than just that simple 12 day cycle. And of course that was based on the cycle of Jupiter. Jupiter takes about 12 years to orbit around the sun. So from earth we would watch Jupiter wander through the stars and it would take it about 12 years to get back to its original state and that's where this 12 year comes from. And then of course we do know the Chinese New Year is actually the second new moon after the winter solstice, so we'll tend to find that in late January or early February as to when that will occur depending on when the new moon was after the winter solstice. So that's defining the new year. When did the new year begin? This is how the new year was then defined. So let's go ahead and finish up with our summary here. The traditional calendar was a lunar solar calendar which date back thousands of years. The typical year would be 12 months while a leap year would be 13 months and we looked at the Chinese zodiac being based on a 60 year cycle. Well that concludes this lecture on the ancient Chinese calendars. We'll be back again next time for another topic in astronomy of other cultures. So until then have a great day everyone and I will see you in class.