January is the first month on the Gregorian and the Julian calendar. It is named after the Roman god of doors, Janus, as this month is a doorway into the new year. Janus is an interesting Roman god as he is two-faced. Thus, he can see both the future and the past. In January, you can see the previous year and view the upcoming one. The old Roman calendar ended in December and did not start up till March. This was changed later with the addition of January to replace March but was made official when the Julian calendar was adopted in 8 BC. The new Julian calendar used the solar cycle rather than the lunar making it more accurate. Unfortunately, its creator Sosigenes, an Alexandrian astronomer who helped create the Egyptian solar calendar, made a small mathematical error of 11 minutes and 14 seconds. Small but significant as the calendar started going out of sync with the solar cycle over time making it hard to use for holy days that required a precise measurement in order to be done at the correct date and time.

This became apparent by the Middle Ages and calls for it to be resolved became more urgent. It was no longer minutes but by then 10 days. This would ultimately result in the Gregorian Calendar (named for Pope Gregory XIII) that was adopted in 1548 by the Catholic church and the Papal States. This resolved the major problem regarding the scheduling of Easter. Since however this was a civic reform, it was up to each nation to decide whether to implement or not. It would gradually be adopted by many countries. Spain was the first to switch over and that included much of Roman Catholic Europe. Protestant countries were not keen on changing right away since the reform was made by the Catholic Church. The British would adopt it 1750 but by a method to avoid saying it was from the Catholic Church. Sweden adopted in 1753. Turkey would switch to using the fiscal year as Gregorian in 1917 and then for the entire calendar in 1926. Russia, under the Communist government, changed in 1918. Greece would change in 1923. Saudi Arabia would formally adopt it in 2016. The change between calendars was startling at first. You might be in November and suddenly thirteen days back in October!

Eastern Orthodox denominations decided for religious purposes to use the Julian rather than Gregorian for their liturgical year (separate from the civic calendar). Which is why in countries  like Greece or Russia the celebration of Christmas and Easter is currently 13 days after it is celebrated elsewhere.

For Further Information

Amy Tikkanen, “Why Does the New Year Start on January 1?,” Encyclopedia Britannica, https://www.britannica.com/story/why-does-the-new-year-start-on-january-1.

“The Month of January,” https://www.timeanddate.com/calendar/months/january.html.

Catherine Boeckmann, “The Month of January 2025: Holidays, Fun Facts, Folklore,” Almanac.Com, last modified January 2, 2025, https://www.almanac.com/content/month-january-holidays-facts-folklore.