《宋书·志·卷十二》
连续考校前后这些影长，以一年中表影最长的那天作为冬至曰，均相差三天?
寻校前后，以影极长为冬至，并差三日。
After examining the shadow lengths before and after the consecutive periods, the winter solstice day is the day with the longest shadow in a year, but there is a difference of three days?