Birthdays are usually celebrated according to the solar or lunar calendar.

Generally, birthdays are mainly based on the lunar calendar, because the tradition of China people is that birthdays are calculated according to the lunar calendar, and two birthdays can be celebrated according to the lunar calendar and the solar calendar. There is a difference between flat leap years in the solar calendar. If birthdays are calculated according to the solar calendar, people born on February 29 in leap years can only have their birthdays once every four years. Besides, people in China can use the zodiac, so the lunar calendar is the best birthday.