The time of calligraphy inscription is generally written in the lunar calendar. The year is the combination of heavenly stems (A, B, C, D, E, Ji, Ke, Xin, Ren and Gui) and earthly branches (Zi, Ugly, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu and Hai).
There are various ways to express dates in paintings and calligraphy works of past dynasties. By understanding the date, we can grasp the styles and characteristics of calligraphers' works in different periods when reading calligraphy with inscriptions, and understand the era and historical background of a calligraphy work, which is helpful to improve our appreciation of calligraphy and painting.