The Hindu Calendar is a traditional system used in India to mark time and organize festivals. It is based on the lunar cycle, which means it follows the phases of the moon. Each month begins with the new moon and has either 29 or 30 days. The calendar includes various festivals, such as Diwali and Holi, which are celebrated at specific times throughout the year. There are several regional variations of the Hindu Calendar, with different names and methods of calculation. Some popular versions include the Vikram Samvat and the Shaka Samvat. Despite these differences, the calendar plays a crucial role in guiding religious observances and agricultural activities in Hindu culture.