According to Western calendar time, the day starts at midnight, which is also known as the prime meridian. This calendar is what we now know as the 24-hour system. In the Eastern calendar, the prime meridian is also used, but there is one important difference to note. Although the Eastern calendar uses the prime meridian, its time units are based on the twelve Earthly Branches. The beginning of the Zi hour, which is between 23:00 and 00:00, is not the start of the next day, but still counted as the same day. The middle of the Zi hour (00:00) marks the start of the next day. Therefore, whether it is considered the previous day or the next day depends on whether it is before or after the Zi hour.

Because the Zi hour belongs to the water element in the Five Elements, girls born during this hour are often smart, graceful, and charming. Their views on love are very clear; they like someone, they will express their feelings directly, and if they don't like someone, they won't hesitate to make their position clear. Girls born during the Zi hour often have many admirers, and they have many choices in love, making it easy to find a compatible relationship. Their future husbands usually come from good families, with good manners, broad-mindedness, and decisiveness, valuing ability. In the interaction between husband and wife, the bond may be stronger than romantic love. They become partners and comrades-in-arms, managing both family and career to grow increasingly prosperous.