《南史·列传·卷七十二》
当初宋元嘉年间，用何承天所制定的历法，比古时十一家都精密。
始元嘉中，用何承天所制历，比古十一家爲密。
In the early years of the Yuanjia era of the Song dynasty, the calendar system invented by He Chengtian was used and was considered more accurate than the 11 other calendars of ancient times.