Zi time: 23:00 - 01:00
Wu time: 11:00 - 13:00

Zi time marks the transition and beginning of each day. A day starts at the beginning of the early Zi time and ends at the end of the night Zi time.
In ancient times, each hour was divided into two periods. Zi time was divided into "Zi Chu" (night Zi time, 23-24 hours) and "Zi Zheng" (early Zi time, 0-1 hour).
Zi Chu (night Zi time, 23-24 hours) belongs to the first day of the twelfth lunar month; Zi Zheng (early Zi time, 0-1 hour) belongs to the second day of the twelfth lunar month.
Since the Yang energy is the weakest when it begins to rise, this moment requires the most protection, and sleep is the best way to nourish Yang. Zi time is also the time of the Yin peak in the Taiji life clock of the day, when Yin energy is the heaviest. Since Yin is still, people should lie still to nourish Yang according to the laws of the rise and fall of Yin and Yang. Due to changes in modern lifestyles, people often stay up late, eat late-night snacks, or engage in various entertainment activities, which can cause great harm to the gallbladder.

The Zi time health preservation method refers to going to bed before 11 p.m. Zi time, as the beginning of the day, is a time when Yang energy is the weakest and Yin energy is particularly heavy, making it the most critical time for the body to be protected. Since Yin is still, this is also the best time to use sleep for health preservation.