相传在4000 多年前的夏朝，即中国历史上第一个奴隶制王朝就开始有了历法(calendar)，后人把当时中国古老的传统历法叫“夏历”。夏历是按月亮的运行周期(rotating cycle) 制定的，故又称作“阴历”。由于夏历中有一年四季节气的变化和农事安排，所以后世又习惯称之为“农历”，字面上的意思是农事月相日历 (moon calendar)，也就是今天所说的“中国阴历”。

译文参考：

According to legend, China's first slave dynasty in history — the Xia Dynasty dating back over 4000 years ago developed the first calendar. The ancient traditional Chinese calendar was later known as the “Xia Calendar”.Since it was based on the rotating cycle of the moon, it is also known as the “Lunar Calendar”. As the Xia revolves around farming arrangements based on the seasons, it is commonly called “Nong Li”, literally the farming moon calendar,also known as the China Lunar Calendar.