天合历仍使用基于东经120°平太阳时间的定朔定气，但采用新法排月，以历月的“对应关系中气”确定月份，雨水为正月，春分为二月，……，冬至为十一月，大寒为十二月，无“对应关系中气”的历月为闰月。一般情况下，每个历月所含的中气就是这个月的对应关系中气，对于双中气月则第二个中气为其对应关系中气，双中气月前面的历月则以该月后面第一个中气为其对应关系中气。(TRW calendar still use Dingshuo longitude 120 degrees flat solar time set based on gas, but using new row to calendar month, "correspondence in" July, rain for the first month, the spring equinox of February,...... As of November, the winter solstice, it is December, no "relationship in the calendar month is a leap month". In general, each calendar month contained in this month is the corresponding relationship between the gas, for the second month in the double gas for the relationship between the gas, in front of the double month calendar month in the first month back in its corresponding relationship in.)