Happy New Year! The month January (originally Ianuarius) is named for the Roman God Janus, who represents beginnings and endings and is often shown with two faces, as with this bust in the Vatican. As months go, January is a latecomer to the calendar party: the Roman Calendar used to consist of ten months beginning in March, which explains why the names of the months September, October, November, and December mean 7th, 8th, 9th, and 10th month respectively. These ten months had a total of 304 days, and then there was an indeterminate period of “winter” (which sounds about right, for those of us living in the northern climes) .
January and February were supposedly added in the 8th century B.C.E, by Numa Pompilius, but that only gave a 355-day year so sometimes an extra month, Intercalaris or Mercedonius, was added. Clearly exactness wasn’t a big deal; to make matters even more complicated, years were sometimes lengthened or shortened for political reasons.
Naming the days of the month was also a little tricky, since days were counted in reference to certain designated days: the first day of the month was Kalendae, Idus fell on the 13th (or, for March, May, July, and October the 15th), and Nonae was the 9th day before Idus. The Romans, however, used inclusive counting so Idus itself would be the first day before Idus. (Inidentally, inclusive counting also explains why Easter Sunday is describe as the 3rd day after Good Friday.) Today, for example, would be the 5th day before Nonae.