Tibetan Calendar is a combination of the lunar calendar and solar calendar. The year which consists of 354 days is divided into four seasons according to the calendar. Unlike most of the other tradition, one year begins with winter and ends in autumn. Twelve months are included in one year and the first month is the same as the Chinese Traditional Calendar. A month includes 30 or 29 days. The former is called the big month while the latter is called the small month. They alternate with each other and an additional one called leap month is added to the calendar to adjust the relationship between months and seasons. According to the Tibetan Calendars, one year is not divided into four equal parts as the time range of each season is based on the locations of the sun in the sky. In general, winter is the longest season, then spring, autumn, and summer. Every 60 years Tibetan Calendar will recount according to the tradition handed down from old times. Besides, the 24 divisions of the solar year could be very useful in predicting the weather of Tibet in the long-term, the planetary motion, and the eclipse.