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:

  1. Day of Light and Dark (and Sun)
  2. Day of Sky and Heaven (and Moon)
  3. Day of Land and Water (and Earth)
  4. Day of Air and Wind (and Birds and Fish)
  5. Day of Animals and Spirits or Angels
  6. Day of Mankind (and Life)
  7. 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.

  • $\begingroup$ The jumping around comes from coverting dates from the Hebrew calendar. Either stick with that, or make everything a fixed date or week+day in the main calendar. $\endgroup$
    – JDługosz
    Dec 29, 2015 at 13:03
  • $\begingroup$ @JDługosz Yes, 14 Nizan (or the Sunday after) used to be the date of Easter in the very beginning of Christianity. I’m more interested in lunar vs. solar, number and lengths of months, month-week alignment, leap rules, likely names of days and months etc. $\endgroup$
    – Crissov
    Dec 29, 2015 at 13:06
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    $\begingroup$ @M.A.Golding Well, the Gregorian Calendar was instituted by a Pope, indicating that they had at least some authority in the area. $\endgroup$
    – Gryphon
    Jul 7, 2018 at 0:16
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    $\begingroup$ @Crissov and in many of the Romance languages, the word for Saturday derives from Sabbath, which is a Christian preservation of a Jewish association. The Portuguese follow a similar pattern to the Latin texts used by the Catholic Church in numbering the days besides Saturday and Sunday. In any case you assume that a "truly and inherently Christian calendar" must have exclusively Christian symbolism in the names. $\endgroup$
    – eques
    Sep 13, 2018 at 16:50
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    $\begingroup$ Most of modern Christianity is in itself "heathen heritage". Are you asking about what sort of calendar would early Christians develop if they managed to avoid any cultural contact for two millennia? $\endgroup$
    – Alice
    Sep 14, 2018 at 8:28

6 Answers 6



Christians have put quite a bit of effort into getting the date of Easter right (though denominations disagree on what "right" is), so any calendar reform is going to have to preserve that. There are two competing goals here: getting the right date, and getting it to fall on a Sunday. These goals are incompatible most of the time, hence the computations involving full moons and equinoxes.

Even while keeping the Sunday goal, the church could have made their calculations easier by saying "first Sunday after 14 (or 15) Nisan", the date on the Hebrew calendar on which the historical event is said to have occurred. Instead, though, the rule is based on the first full moon after the vernal equinox. Why not follow the Hebrew calendar? Partly because the early church wanted to distinguish itself from what came before (consider "old testament" and the theology that it's less important now), and partly because the church would be unlikely to want to tie itself to a system/group that it has at times been extremely hostile toward. You don't want to use the other group's system that you're trying to move away from; you want your own system. Unless these aspects of the church have changed in your alternate history, we should therefore assume that the Christian calendar will continue to avoid using the Hebrew calendar as a basis.

But you are still likely to have the concept of months. They're convenient in a way that "week 37" (or whatever) isn't. Lunar cycles are visible signposts of the passage of time. And the bible talks about new moons as significant days (though there is some dispute about how much of which parts of the Hebrew bible Christianity would care about).

I think it plausible that a new Christian calendar would develop its own lunar calendar. There are at least two examples to look at, the Hebrew calendar and the Muslim calendar -- the difference between the two is that the former uses leap-months to keep special days in their proper seasons (a solar-adjusted lunar calendar), while the latter is purely lunar. As far as I understand, Christianity has only two important dates that need to stay in their proper seasons, so they could adopt a pure-lunar calendar with the seasons of Easter and Christmas fixed, rather than their months. Or they could implement something similar to the Hebrew calendar, but they'd call it something different.

If you don't care about the month names for the holidays -- if Easter doesn't have to be in "April" or "Nisan" but just needs to be in the northern spring -- then you are free to have any number of months you want, though to approximately align them with the year you'll need 12 or 13. What would they name them? One possibility is "first month", "second month", etc, particularly if those turn into single words in Latin or Greek. "First month" should probably be the month containing Easter, since that's the transformative event of Christianity. Another possibility is to name the months after the disciples. (I think that more likely than naming after the tribes of Israel, a connection that Christianity might want to downplay.) If you include Judas's replacement, you can even get up to 13, for those years when you need a 13th month. (Maybe the leap-moth is Judas, so doesn't show up as much.)

If we're naming months after disciples, one might ask, shouldn't we name one after their teacher/leader, Jesus? To some Christians using the name of their savior in casual conversations ("your dentist appointment is on Jesus 12th") would seem inappropriate, even blasphemous, so I expect they would avoid doing so.


The seven-day week is fundamental to Christianity, based on the seven days of creation at the beginning of Genesis. We have a problem here, though; the seven days of creation culminate with the sabbath, Saturday, while Christianity's special day is Sunday, the "lord's day". (I'm not a church historian, but I've read that they originally celebrated the sabbath on Saturday, as do Jews, but then moved the focus to Sunday to distinguish their community. Plus, maybe that Easter thing.) This might mean that they won't want a close naming tie to the days of creation because it puts the emphasis on the wrong day. On the other hand, I have been told (h/t eques) that some Christians see Sunday as the beginning of a new creation-like cycle, so maybe that's ok. You'll have to figure out how this works in your world. Let's look at alternate schemes for day names.

You could instead look for a different set of seven to use as day names. I suggest you name the days after the seven cardinal virtues, to keep Christian values front and center every day. (You could also consider Paul's seven spiritual gifts, but I don't think they're as widely known.)


Putting these ideas together, here is one possible calendar. (I don't know the significance of most of those disciples, so I haven't attempted a complete ordering.)

Days of the week:

  • Chastity
  • Diligence
  • Patience
  • Kindness
  • Temperance ("good Friday" falls on Temperance, for abstinence)
  • Charity
  • Humility (the "lord's day")

Months of the year (not in order):

  • Peter (contains Easter, because he figured prominently in the events there)
  • John (contains Christmas, because some say he's the "beloved disciple" so he should get something special)
  • Judas, when a leap month is needed; goes right before Peter/Easter month
  • distribute the other nine original disciples and Judas's replacement as you like; I don't know if any of them have seasonal or sequential connections
  • $\begingroup$ I don't think the Sabbath is as big of a problem as you think it is. Consider the Spanish names for the weekend days, "Sábado" and "Domingo". These are clearly "Sabbath" and "The Lord's Day". Spain has a particular reputation for being strong when it comes to religion (as in "Spanish Inquisition") so if this is good enough for them, everyone else should be fine with it. $\endgroup$ Sep 13, 2018 at 17:58
  • $\begingroup$ @MontyHarder thanks for the information. I'm mainly influenced by Christianity in the US, where there is a history of things like pressuring businesses to not open on Sunday because it's the sabbath, barring alcohol sales, discouraging some recreational activities, etc. Perhaps that's atypical and, as an outsider, I couldn't tell? $\endgroup$ Sep 13, 2018 at 19:29
  • $\begingroup$ Let us continue this discussion in chat. $\endgroup$
    – eques
    Sep 13, 2018 at 20:35
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    $\begingroup$ @MonicaCellio Sunday as Sabbath is not universal to all of Christianity. Even when Catholicism was very heavily dominant, all you could really say is "according to the official Catholic stance...", and not "According to Christianity..." Anecdotally: as a pious Christian with Christian family and who prefers to associate with other pious Christians, I would say that most everyone I know who would have an opinion would cite Saturday as Sabbath, and I cannot think of anyone who I know would claim it as Sunday. And I know a lot of Christians of various denominations. $\endgroup$
    – Loduwijk
    Sep 15, 2018 at 16:44
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    $\begingroup$ @Aaron but Sunday is still the "big" day of the week in Christianity, so the sabbath isn't the highlight of the week. That's why I argued against day-names that follow the creation story; Christianity (I think in general?) wants the focus to be on Sunday. Is there something in my answer that isn't clear enough that I can fix? Thanks. $\endgroup$ Sep 16, 2018 at 2:14

Lets assume that this hypothetical calendar did do as the question suggest and have no months (after all, Genesis mentions seasons, days and years are created, not months).

Dates would be referred to with the number of the week and day, and weeks of the year would mark important masses and passing of seasons. One problem with this is that the number of days a year (~365.25) is not evenly divisible by 7, and there would be one or two extra days per year that is "left over". Either a new year would not start on the first day of the first week every year (imagine if the year started on the 2nd of January), or one-two extra days would have their own tiny-week, or a year would consist of 52 weeks most years and a full leap-week every five or six years.

Some other ideas about a truly and inherently Christian calendar:

  • Weekdays would be namned to suit the christian mythos (maybe naming the first day lightday since light was created on the first day, and/or a Johnsday after John the Baptist).
  • The reason for christian easter can only have happened once, so it is possible the easter week (and the holy week and so on) would happen the same days every year. That is, given that we somehow know (or arbitrary decide) which year of the hebrew calendar that the crucifixion of Jesus happened, we can translate that years easter to a specific date in the hypothetical calendars corresponding year. Once we done that, the new date could potentially be used every year.
  • The new year would either still be close to the birth of Jesus (such as the day itself, first of advent, or the epiphany) or close to (the-non-moving) easter.
  • $\begingroup$ Easter moves because it's trying to match a date in a lunar calendar system from a solar calendar. You'd still have that problem unless you just ignored it and fixed it arbitrarily. You may as well just have the year divisible by seven days, it'll be a few years before there's a noticeable error, chuck in a holy week (or month) and reset it (the Jewish calendar has a leap month). $\endgroup$
    – Separatrix
    Dec 29, 2015 at 16:25
  • $\begingroup$ @user16295 I edited to explain further what I meant with a fix date for Easter. If one can not decide on an year for the crucifixion, the choice would indeed be arbitrary. $\endgroup$ Dec 29, 2015 at 16:43
  • $\begingroup$ Eater also moves because the early Christians concluded it was more important that Easter be on a Sunday (as the Gospels indicate) $\endgroup$
    – eques
    Sep 13, 2018 at 16:47

It would be reasonable to name the days according to the Easter cycle. After all, Easter events are strictly attached to days, not dates.

For example, Russian name for Sunday is воскресенье (voskresenie, literally Resurrection).

In this line Monday may become Appearance (re: Thomas), Tuesday is Transfiguration (if I didn't miscalculate), Thursday shall be Ascension.

I am not that well versed to suggest other days.

PS: Russian for Saturday is суббота (subbota i.e. Sabbath).

  • $\begingroup$ Something like Sabbath (eg. sobota) seems to appear at least in most Roman and Slavic languages. $\endgroup$
    – BartekChom
    Dec 30, 2015 at 19:15

Weekdays would likely be named according to Genesis events:

  1. Day of Light and Dark (and Sun)
  2. Day of Sky and Heaven (and Moon)
  3. Day of Land and Water (and Earth)
  4. Day of Air and Wind (and Birds and Fish)
  5. Day of Animals and Spirits or Angels
  6. Day of Mankind (and Life)
  7. Day of Rest (and God), Sabbath

When I look up the Genesis creation narrative, it says that the Sun and Moon weren't created until the fourth day (Genesis 1:16). The waters and sky were created on the second day. What's your citation for them being created on the first and second days? I checked multiple online bibles (including Catholic and Latter Day Saints versions) and they were consistent on this. Similarly, the birds and fish were created on the fifth day; both animals and humanity were created on the six day.

It's worth noting that the Jewish calendar did not name any day other than the Sabbath. This may be why the Christians chose to use local names instead:

  1. Sun day
  2. Moon day
  3. Tyr's day
  4. Odin's day
  5. Thor's day
  6. Freya's day
  7. Saturn's day

I leave it up to someone else to explain why they chose two heavenly objects, four Norse gods, and one Roman god.

If you want Christian English names rather than the Jewish numbers, an alternative naming:

  1. Lightday
  2. Skyday (also water)
  3. Landday (also the seas)
  4. Starsday (also the Sun and Moon)
  5. Fishandfowlday
  6. Lifeday (including the animals of the land, humans, and plants)
  7. Restday

If you want your story to change the bible, that's fine, but you should say so explicitly. Your version certainly makes more sense than the original with its sourceless light and water world.

The numbered days of the week suggest that the month days might also be named as numbers. The Romans did. We still use September (7), October (8), November (9), and December (10) from the Roman calendar. Your Catholics could use those ten names plus Birth month and Resurrection month. Note that translating the bible out of Latin is a relatively modern thing. Latin was the priestly language for a thousand years of Christian history.

Superficially having twelve months and twelve apostles would seem to fit, but I don't see them ignoring Jesus that way. Both the birth and resurrection seem worthy of their own months compared to mere apostles. Even lesser miracles like walking on water and changing water into wine seem like they might be more important. So perhaps

  1. Birth month
  2. Wine month (water into wine)
  3. Healing month (many occurrences)
  4. Exorcism month (several occurrences)
  5. Raising month (several occurrences)
  6. Calm month (calming the storm and the apostles' fears)
  7. Feeding month (the division of the loaves and fishes; catching 153 fish)
  8. Waterwalking month (walk on water)
  9. Coin month (sent Peter to catch a fish with a coin its mouth to pay their taxes)
  10. Curse month (cursed a fig tree with no fruit)
  11. Resurrection month
  12. Ascension month

This divides the miracles into groups. Some are singular while others are repeated (most notably healing). I would say that Crucifixion day (Good Friday) would be the first day of winter, that is to say, around our December 22nd. That would allow Lazarus day (first day of summer) to occur near the end of Raising month.

Winter: Ascension; Birth; Wine Spring: Healing; Exorcism; Raising Summer: Calm; Feeding; Waterwalking Fall: Coin; Curse; Resurrection

Each season might be associated with a Gospel apostle. Fall could be Matthew (taxes are collected in Coin); Winter could be Mark (the oldest gospel); Spring could be Luke; Summer could be John.

  • 1
    $\begingroup$ Yeah, my knowledge of the Bible is limited and I may have confused things I looked up when I originally made that list.Note that the Germanic gods make more sense when you look at their Roman/Greek counterparts, because they share names with planets, e.g. god of war: Tyr/Diu = Ares/Mars, hence English Tues-day = French Mar-di and symbol ♂, see e.g. Wikipedia for more. $\endgroup$
    – Crissov
    Dec 31, 2015 at 17:41

There is no such thing as a 'purely Christian' calendar because there is no such thing as a 'purely Christian' religion.

All religions and cultures are heavily influenced by religions and cultures around them. If it wasn't for Christianity's adoption as the official religion of the Roman Empire, it would not have evolved in the way it did, and would have instead changed in ways we cannot predict. Christmas was drawn from pagan solstice celebrations. Easter was born from Passover and other spring fertility celebrations.

To remove the external influences from the calendar you first have to remove the external influences from Christianity itself, and once you do that you're left with nothing at all.


It would be a lunar calendar based on the Jewish Calendar

Many Christian events are based around the timing of Easter which is closely tied to the Hebrew celebration of Passover. Easter happened on the first day after the Passover Sabbath. Since the Sabbath is always a Saturday then Easter is always a Sunday.

The Hebrew calendar already has the 7 day week and naming for the days and the lunar cycles.

Christians may have also carried over the idea of special years from the Old tenement commandments such as the Jubilee year (year of returning land and forgiving debts) as well as the numerous festivals and sacrifices prescribed in the old testament. All of which are based on this lunar calendar.

  • $\begingroup$ In our world the church took steps to distance itself from Judaism and its calendar; for example, the calculation of Easter is complex compared to just following the Hebrew calendar, but they chose to do it anyway. I believe this is for theological reasons -- that whole supersession idea is pretty important. How do you see a Christian calendar based on the Jewish calendar developing? $\endgroup$ Dec 9, 2016 at 3:06

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