A solar calendar is a system for measuring time based on the Earth's position in relation to the Sun. It divides the year into months and days, aligning with the solar year, which is approximately 365.25 days. This type of calendar helps track the seasons, making it useful for agriculture and cultural events. The most widely used solar calendar is the Gregorian calendar, introduced by Pope Gregory XIII in 1582. It consists of 12 months and includes leap years to account for the extra quarter day. Other examples of solar calendars include the Julian calendar and the Persian calendar, each with unique features and historical significance.