The Gregorian calendar is the most widely used civil calendar in the world. It is a solar calendar that is based on the Earth's orbit around the sun. The calendar is named after Pope Gregory XIII, who introduced it in 1582 to replace the Julian calendar. The main difference between the two calendars is that the Julian calendar was slightly longer than the actual solar year, so over time it became increasingly inaccurate. The Gregorian calendar was designed to more accurately reflect the solar year, and it is the calendar that is used in most countries today.
The lunar calendar, on the other hand, is a calendar that is based on the phases of the moon. It is also known as a lunar calendar or a lunar-based calendar. The lunar calendar is used in many cultures and religions around the world, including Islam, Judaism, and various Eastern religions.
One of the main differences between the Gregorian calendar and the lunar calendar is the length of their respective months. In the Gregorian calendar, months are based on the solar year and have a fixed length of either 28, 30, or 31 days. In the lunar calendar, months are based on the phases of the moon and have a variable length that can range from 29 to 30 days. This means that the lunar calendar is not as closely tied to the solar year as the Gregorian calendar.
Another difference between the two calendars is the way in which they mark the passage of time. The Gregorian calendar is divided into 365 days per year, with an extra day added every four years to account for the fact that the solar year is slightly longer than 365 days. The lunar calendar, on the other hand, is based on the cycles of the moon, with each month beginning on the new moon and ending on the full moon.
Overall, the main difference between the Gregorian calendar and the lunar calendar is that the former is based on the solar year and has a fixed number of days per month, while the latter is based on the phases of the moon and has a variable number of days per month.