When is the fourth departure day?

The day before vernal equinox, autumnal equinox, summer solstice and winter solstice.

The day before the vernal equinox, autumnal equinox, summer solstice and winter solstice in 24 solar terms is called departure from the sun in mathematics. There are four such days throughout the year, so it is called four days off.

The day before the vernal equinox is called "Li Mu"; The day before the summer solstice is called "fire prevention period"; The day before the autumnal equinox is called "golden calendar"; The day before winter is called "water separation". "One day is worth four days, don't spend it on big things." All such matters as moving into a house, installing beds and doors, getting married, breaking ground to build a house, opening a business, etc. Can't use it for four days. The four trips are on the day before the vernal equinox, autumnal equinox, summer solstice and winter solstice.