After the adoption of Christianity as the one official religion in late Ancient Rome, the new role of pope inherited some duties of previous leaders, among them he’s responsible for the calendar. The last time this authority was notably enacted was with the reforms of Gregor XIII in 1582, which changed the leap rule (+4/–100/+400) and the Easter computus. The start of the year (when the year count is incremented) wasn’t decreed and the now canonic 1 January was adopted at very different times.
The Roman calendar used to have strong lunar properties but became more and more solar over time. Some things had become mere tradition so that they could be changed, which (among others, but most prominently) Julius Caesar did. This was not the only calendar that early Christianity developed with, however – the lunar Hebrew calendar in particular, due to its use by Jews, and the Egyptian calendar which informed the Coptic calendar with its 12×30-day months and 5–6 extra days which is still in Christian use.
Except for short-lived solitary French and Russian revolutionary attempts, there has been no real calendar reform in over 400 years, at least in the Christian parts of the world. It was last tried with a global scope after WW2 with the World Calendar and competing proposals, which finally failed due to religious concerns about days outside the week cycle. There have been some minor secular changes or additions mostly for business or technical purposes, especially the start of the week being Monday (not Sunday) in international standard ISO 8601 and its predecessors (which also effectively introduce a parallel leap-weak calendar).
Since the date of Easter is not fixed within the civil calendar (and still differs between Western and Eastern churches) and most names and numbers seem arbitrary with lots of “heathen” heritage, I came to wonder:
What design features would a truly and inherently Christian calendar exhibit?
To me, the only things that seem to be required are a 7-day week (although additional sabbaths may be possible) and some way to associate Easter with a full moon around the Northern spring equinox. The names of pagan gods would not appear in month or day names.
Weekdays would likely be named according to Genesis events:
- Day of Light and Dark (and Sun)
- Day of Sky and Heaven (and Moon)
- Day of Land and Water (and Earth)
- Day of Air and Wind (and Birds and Fish)
- Day of Animals and Spirits or Angels
- Day of Mankind (and Life)
- Day of Rest (and God), Sabbath
The names of the twelve months – albeit less or more possible, even none – could be derived from the Israelite tribes (i.e. Jacob’s sons) or from Jesus’s first apostles, but there may be better options.
Also, would it matter much when it was to be designed and implemented in an alternate timeline, e.g. around 0400 (~ 1st Council of Nicaea, split Roman Empire), 0800 (~ 2nd CoN, Charlemagne), 1200 (Europe christianized), 1600 (~ Gregor XIII, reformation, colonization) or 2000 (~ now)?
Disclosure: I’ve published earlier attempts of mine at Wikia.