Some Christian writers considered the possibility that pagan commentators may have mentioned this event, mistaking it for a solar eclipse - although this would have been impossible during the Passover, which takes place at the full moon. Christian traveller and historian Sextus Julius Africanus and Christian theologian Origen refer to Greek historian Phlegon, who lived in the 2nd century AD, as having written "with regard to the eclipse in the time of Tiberius Caesar, in whose reign Jesus appears to have been crucified, and the great earthquakes which then took place"