Dating the Birth of Jesus Christ on Hanukkah

Abstract

The still controversial date of the birth of Jesus Christ (Nativity Day) is investigated by using multidisciplinary elements: historical tradition, ancient calendars (Julian and luni-solar) and astronomical calculations. The Nativity Day dates of Western—December 25—and Eastern traditions—January 6—have been compared with Kislev 25, the initial day of the Jewish feast Hanukkah, reported in an ancient source of the IV century as the Nativity Day. The same source sets the Epiphany on Tevet 6. Astronomical calculations allow us to reconstruct moon phases and ancient luni-solar calendars, and to verify whether Hanukkah can be associated to the Nativity Day of the Christian tradition. By considering the leap years wrongly introduced in the first decades of the Julian calendar, and the flexibility of the Jewish luni-solar calendar of 2000 years ago—regarding the beginning of months and embolismic years—our astronomical calculations show that the Nativity Day set on Kislev 25 is compatible with the Eastern tradition, 6 January 1 after Christ, in agreement with the year calculated by Dionysius Exiguus. Moreover, also the Epiphany is compatible with the Eastern tradition of January 6, if it is set on Tevet 6 of a year later, just in the day indicated by an ancient source of the IV century.