Although Livy's Numa instituted a lunar calendar, the author claimed the king had instituted a 19-year system of intercalation equivalent to the Metonic cycle centuries before its development by Babylonian and Greek astronomers.
Meskipun menurut Livy, Numa melembagakan kalender lunar, penulis itu mengklaim raja telah menetapkan sistem interkalasi 19-tahunan setara dengan Siklus Metonik berabad-abad sebelum perkembangannya oleh astronom Babilonia dan Yunani.