Does the eight-character year start from birthday or Chinese New Year?

The year of the constellation does not start from the birthday, nor from the China New Year, but from the holiday time that begins in spring. For example, according to traditional festivals, people born on the fifth day of the first lunar month in 1995 belong to the Year of the Pig. But for the eight characters, the birth time has not been in beginning of spring (Gregorian calendar 195-02-04 15:), so the year of the eight characters is 1994 (JOE), not 1995 (B Sea).