Ancient calendars were systems used by early civilizations to track time, seasons, and agricultural cycles. Different cultures developed their own calendars based on celestial events, such as the phases of the moon or the position of the sun. For example, the Mayan calendar included a 260-day ritual cycle and a 365-day solar year, while the Egyptian calendar was based on the annual flooding of the Nile River. These calendars played a crucial role in organizing daily life, religious events, and agricultural activities. The Roman calendar, which evolved into the modern Gregorian calendar, originally had ten months and was later adjusted to include January and February. Each ancient calendar reflects the unique environment and cultural practices of its society.