「甲寅太乙曆」是作者根據唐代「太乙金鏡式經」中記載的一條上元積年數據發 現並修復的一部曆法。它可能太以術數中的第一部曆法。 在重構這部曆法之上員的過程中，意外地發現，就氣朔的推算來說，「甲寅太乙曆」與 「殷曆」實際上是相同的。由於兩曆都是四分曆，是故他們推算的曆譜將是完全一樣的。「甲 寅太乙曆」的制定年代大約出於400 BC前後，最遲當不晚於漢武帝元朔元年（128 BC）。 「甲寅太乙曆」中有三個大的周期，這三大周期是「甲寅太乙曆」上元的選擇所必須考 慮的先決條件，它們分別是：4560年的氣朔周期，4320年的大游太乙周期，以及225年的 五福太乙周期。而後兩個大的周期是普通的官方立法所不予考慮的，因此，官方曆法無法取 代太乙曆法。 由於太乙曆法得上元選擇法採用的是中國古代傳統數理天文學中的演紀算法，這個事實 從未引起研究者的注意，因此，可以說太乙曆法是中國曆法史上長期以來被忽視了的一個重 要分支。

　　　　　Based on a few historical materials in a book of the Tang dynasty, a calendar, named the Jiayin taiyi li（甲寅太乙曆）, is found. It may be the first calendar of taiyi method（太乙術數）. Because of its fundamental constants and epoch of month and year are the same with Yin li（殷曆）, the arrangement of qi（氣）and the new moon of Jiayin taiyi li must be the same as Yin li. The Jiayin taiyi li was probably compiled around 400 BC, at latest it appeared before 128 BC. The superior epoch of this calendar composed of three big cycles which are 4560 years for the cycle of year and month, 4320 years for the cycle of dayou taiyi（大游太乙） and 225 years for the cycle of wufu taiyi（五福太乙）. The last two cycles were never included in the calendar of government. It shows us that the calendar used in the taiyi method is different from the calendar issued by government. Because the selection method of its superior epoch in the taiyi li is the traditional method of ancient Chinese mathematical astronomy, the calendar of taiyi is an important branch of history of Chinese calendrics, which has been neglected by historian for many years.