https://en.wikipedia.org/wiki/Chinese_calendar
The traditional Chinese calendar (also known as the Agricultural Calendar [農曆; 农历; Nónglì; 'farming calendar'], Former Calendar [舊曆; 旧历; Jiùlì], Traditional Calendar [老曆; 老历; Lǎolì]), is a lunisolar calendar which identifies years, months, and days according to astronomical phenomena. In China, it is defined by the Chinese national standard GB/T 33661–2017 ...