Who was the Gregorian calendar founded for?

The history of the Yellow Calendar is very long.

The Gregorian calendar, also known as the old Gregorian calendar and the imperial calendar, was born on the basis of the China lunar calendar, and it is a perpetual calendar with good and bad luck every day. According to legend, the yellow calendar was created by Xuanyuan Huangdi, so it is called the yellow calendar.

China perpetual calendar