Which country invented the lunar calendar we use today?

The Xia Dynasty began the summer calendar.

The summer calendar is one of the traditional calendars in China, also known as lunar calendar, lunar calendar, ancient calendar and old calendar. Belongs to a kind of lunar calendar, the average calendar month is equal to a new moon, which is the same as the lunar calendar principle, so it has the composition of lunar calendar; On the other hand, the leap month is set to make the average calendar year the tropic year, and 24 solar terms are set to reflect the changing characteristics of the seasons (the annual movement of the direct point of the sun), so there is also a solar calendar. Today, almost all Chinese in the world, as well as countries such as the Korean Peninsula and Vietnam, still use the summer calendar to calculate traditional festivals such as Spring Festival, Mid-Autumn Festival and Dragon Boat Festival.

The lunar calendar in astronomy mainly refers to the calendar arranged according to the cycle of the moon phase [1]. The calendar of the moon's one-week orbit around the earth (taking the sun as the reference object, the actual moon's orbit is more than one week) is January, that is, the first month of the lunar calendar is used as the basis for determining the calendar month, and a year is twelve calendar months. In agrometeorology, the lunar calendar is commonly known as lunar calendar, lunar calendar, ancient calendar and old calendar, which refers to the traditional summer calendar in China. Astronomically speaking, the summer calendar is actually a kind of lunar calendar.