Is beginning of spring a whole day or an hour?

All day. Every year on February 3rd to 5th in Gregorian calendar, beginning of spring is from 0: 00 on February 3rd to 23: 59 on that day. This whole day can be said to be beginning of spring. Beginning of spring is the first of the 24 solar terms, and it starts at four o'clock in a year. "Li" has the meaning of beginning, and "beginning of spring" has opened the prelude of spring, marking the arrival of spring when everything is revived.