What's the difference between Tibetan calendar and lunar calendar?

There are also some subtle differences between Tibetan calendar and lunar calendar. First of all, the Tibetan calendar does not take the new moon as the first day, and the full moon is fixed at 15, so sometimes it differs from the lunar calendar by one or two days. Secondly, the Tibetan calendar is different from the lunar calendar, so sometimes the leap year differs from the lunar calendar by about one month, but the year is exactly the same as the lunar calendar. In addition, there are two dates in the Tibetan calendar in order to configure the solar day as a date series corresponding to the lunar calendar. The so-called "double date" literally means redundant date, that is, this date series (date) has to be repeated once. The so-called lack of days means that this date series (date) should be skipped and left empty. Generally, there is a shortage of 1-2 days a month, about 14 or 5 days a year, and only five or six days a year. The month in which there is neither a heavy day nor a short day is called Ji Yue.

Compared with the lunar calendar, the Tibetan calendar was born in the plateau area with special climate, so there are some special places to adapt to the local climate characteristics. Instead of simply dividing the years evenly, it calculates according to the fixed point of the "sun" (that is, the position of the sun), organically combines the data with the changes of various birds and animals in Tibetan areas, determines the solar terms and divides the seasons. Therefore, although the Tibetan calendar is divided into four seasons: spring, summer, autumn and winter, it is divided into six seasons according to the unique climate characteristics of the region, namely, spring, late spring, summer, autumn, winter and late winter. On the whole, winter is the longest, followed by spring, autumn and summer. In some high mountain areas, there is even no summer, and spring and autumn are connected.