The Buddhist calendar is the system of calendars used by Buddhist communities, mostly in East Asia but also across South Asia and Southeast Asia. It is based on the traditional calendar of India and varies from country to country. In Buddhist countries, it is often used to mark important festivals and holidays. The Buddhist calendar keeps track of the days, months, and years as they pass. It is different from the regular calendars because it is based on a lunar cycle that is shorter than the solar cycle that most other calendars use. The months of the Buddhist calendar start when the moon is full, and end when the moon is dark. Each month is usually made up of 29 or 30 days.