Four o'clock, eight quarters, twenty-four hours, seventy-two hours.

Four seasons: spring, summer, autumn and winter.

Section 8: beginning of spring mayor Xia Liqiu beginning of winter vernal equinox autumnal equinox summer solstice winter solstice.

Seventy-two waiting periods, five days as one waiting period, three waiting periods as one section, six waiting periods as one section, and seventy-two waiting periods as one year.

Wood is straight, roots and branches spread and grow around, and wood represents spring.

Under the wet moon, winter is the time when everything hides. The spirit of the sun sinks, the air of the earth drops, the air drops, hides and converges. Water has this characteristic, so it is represented by water.

The alternation of spring, summer, autumn and winter is the change and movement process of natural qi. The ancients used the five elements to explain this change more vividly.