Why is there a difference between the lunar calendar and the national calendar?

Because China has a lunar calendar and a solar calendar, every day has its corresponding date in the solar calendar and also has its corresponding date in the lunar calendar. Lunar calendar and solar calendar run according to their own laws and cycles, so every day has the date of lunar calendar and the date of solar calendar. In the past, old people recorded their birthdays in the lunar calendar, but now, in many cases, it is necessary to fill in the date of birth. If they write in lunar calendar, there will be many misunderstandings. So they usually write in the solar calendar, so everyone has a lunar birthday and a solar birthday. In addition, some fortune tellers also use the birthday of the lunar calendar.

I don't know the origin. .