Sextus Julius Africanus further refers to the writings of historian Thallus: "This darkness Thallus, in the third book of his History, calls, as appears to me without reason, an eclipse of the sun. For the Hebrews celebrate the passover on the 14th day according to the moon, and the passion of our Saviour falls on the day before the passover; but an eclipse of the sun takes place only when the moon comes under the sun." Christian apologist Tertullian believed the event was documented in the Roman archives.