When I was a child, it was April 5th in Tomb-Sweeping Day. How can it be April 4 now?

Tomb-Sweeping Day is one of the twenty-four solar terms, which generally falls from April 4th to 6th every year according to the China lunar calendar.

In the past, Tomb-Sweeping Day was celebrated as a fixed festival, without considering the tradition of the China lunar calendar. Now Tomb-Sweeping Day has lived according to the solar terms. So many calendars of electronic products such as mobile phones are displayed according to the past settings.