R is for rùn 闰 (leap year)

We have an exciting science lesson today! It's about the traditional Chinese calendar - lunar calendar, which is based on the phases of the Moon.

In lunar calendar, a lunar month is the time between two new moons or full moons, which is 29.5 days. I showed them a video by history channel about moon phases and demonstrated with globe, flashlight and a pingpong ball as the moon.

So why does Chinese New Year fall on different days each year? Because Chinese look at the moon. Winter solstice is on 21st or 22nd of December. This is the shortest day in the northern hemisphere. The second new moon after winter solstice is the first day of Chinese new year. The next full moon is the last day of Chinese new year, which is the Lantern Festival.

Look at these two moon phases calendar in Jan. and Feb. of 2013:

 

  

The shortest day in 2012 is Dec. 21st. The first diagram shows that the first new moon after Dec. 21st is Jan. 11th, 2013 and the second one shows the second new moon is on Feb. 10th, which is the first day of Chinese New Year. The next full moon, which is on Feb. 25th, is the last day of Chinese New Year, which is the Lantern Festival. 

So today's class is actually about lunar calendar, not about leap year. The calculation of leap year would be too hard for them. The essential question for today's class is how moon changes. We did a fun craft to demonstrate moon phases. They used yellow paper to represent sun, red strips as light, a green circle as the earth and black and white as moon phases.

I ask them to observe the moon on Feb. 25, which is the last day of Chinese New Year, and see if the moon is big and round, because that day is a full moon.

I love Chinese way to determine the calendar, which is more correct in terms of seasons. In China, we never say Chinese New Year. Instead, we call it Spring Festival. Because the second new moon after the winter solstice is the beginning of spring.