- A: Started in the 3rd/4th century. This is by lunar vs solar calendars, equinoxes and solstices, and the meaning of genesis.(edited)
- Dating
- December 25th as the birth date of Jesus was attested prior to AD 274. Hippolytus’ Commentary on Daniel (written sometime between 202 and 211) claimed that Jesus was born on December 25th and was crucified on March 25th. Then in his Canon he produced a lunar table (dating astronomically to 222) which he used to compute the dates of Passover from creation onward. This chart gives March 25th as the date of the crucifixion, which is the date of the vernal equinox, and this is the date that corresponds to the creation of the world (so Jesus died on the anniversary of the world’s creation), which was backdated from the date of the first Passover in the first week of creation. The Canon gives April 2, 2 BC as the date of Jesus’ conception (γένεσις) but there is also a two-year discrepancy in his age. Thomas C. Schmidt notes that lunar table gives March 25th as the date of Jesus’ conception if Jesus were born two years earlier (Commentary on Daniel also gives the date of Jesus’ birth as 4 BC if reckoned from his age and 2 BC if reckoned from Augustus’ reign). In support of this, Hippolytus’ Chronicon says that Jesus was born 5,502 years from the creation of the world, while Commentary on Daniel says that this occurred 5,500 years from creation. Thus, the chronology in Commentary on Daniel appears to use the same lunar computations that later appeared in Canon, and shows the same 2-year discrepancy, though it is unclear why he waved in his dating of the year of Jesus’ birth. The Chronicon also implies that Jesus was born nine months after he was conceived, with the date of the birth given as 5,502 years and nine months from creation. Nine months from March 25th would give the date of Jesus’ birth as December 25th.
- Apparently, the passage of Hippolyus of Rome is an interpolation according to (Roll, Towards the origins of Christmas pp.79-81, especially p.80 n.106). The author claims that Jesus was born in the 42nd year of Augustus’ reign, on Wednesday the 25th of December. The problem is that Augustus ruled only 40 years and the author might conceivably have imagined Augustus’ reign as beginning in 44 BCE, immediately after Julius Caesar’s death (which already suggests a later, poorly informed, author): in that case he would mean 1 BCE; that year 25 December fell on Saturday by modern reckoning, or within a day or two of that by Roman reckoning (Roman reckoning wasn’t fully in synch with modern reckoning until 8 CE) — certainly not a Wednesday.
- The interpolator goes on to claim that Jesus died aged 32 (‘in his 33rd year’) on Friday 25 March in the 18th year of Tiberius’ reign, in the consulship of Rufus and Rubellio. ‘Rufus and Rubellio’ are already errors — for C. Fufius Geminus and L. Rubellius Geminus. Their consulship was in 29 CE, and 25 March did fall on a Friday that year, so we’re looking good so far. However, The 18th year of Tiberius’ reign didn’t begin until September 31 CE, which puts Jesus’ death date in March 32 CE. If Jesus were born on 25 December 1 BCE, then being aged 32 would put the death date in March 33 CE.
- So I guess that would make the earliest mention of December 25 as Jesus’ birthday coming from a mid-fourth-century Roman almanac that lists the death dates of various Christian bishops and martyrs. The first date listed, December 25, is marked: natus Christus in Betleem Judeae: “Christ was born in Bethlehem of Judea.