kengr

Now let's get into the fun relationships between various religions and the clock/calendar and how this can mess things up on other planets.

The various Abrahamic religions (Judaism, Christianity and Islam) all have their own calendars, with various relationships to the sun and moon. The Baha'I have yet another calendar, but share the 7-day week with the other three.

Judaism and Islam have the day starting with sunset. *Actual* sunset.

This led to problems when Jews started living around and above the Arctic circle. As I understand it, this led to a ruling that in cases where the sun is not practical to use, you use the sunset in Jerusalem.

To the best of my knowledge, Islam has not yet dealt with this.

Christian monks were one of the drivers behind clocks in the Western world, so the Catholic church and its descendants pretty much run on clock time, not solar time. The Liturgy of the Hours (and the canonical hours based on it) follow clock time for the most part.

Islam definitely runs on solar time. There's a simple test for when the daylight (and thus things like the daylight fasting in Ramadan) begins. It's when you can tell the difference between a white thread (hair) and a black one laying in the palm of your hand. A quick search for an equally clear definition of sunset didn't turn up anything equally simple, but from the learned arguments I encountered, it is most definitely an *observation al* event, not a calculated or clock based one.

Islamic prayer times are equally tied to the sun.

So what Moslems on Mars or some planet around another star will do is unknown. If I had to guess, they might go with Mecca the way Jews did with Jerusalem. Or they might go with local solar time.

Now we have the week. this gets *really* problematic, because it's supposed to be important to take a *specific* day of the week as a day of rest. No putting it off or doing it early. It has to be *that* day.

Now, using Mars as an example, from my previous post, we know that 36 Martian sols is a bit over 37 days. Which means that you'd be taking that day of rest a day late! Not good.

Trying to stick with the earth-based week for this will be a pain. And various religious authorities *will* Have Opinions On This.

Beyond the week we've got months and various holy days (holidays) based on the year.

The Gregorian calendar is fairly straightforward, though the rules for locating various feasts such as Easter (which determines when a whole *bunch* of things happen) and various saints days are anything but. Easter is based on some arcane calculations that are an approximation of determining the first Sunday after the first new(?) moon after the spring equinox.

Try transplanting *that* to Mars or elsewhere!

The Jewish calendar is a hybrid lunar/solar calendar that has a roughly 19 year cycle in which leap *months* are inserted according to various rules. This *could* be transplanted, but the difference between a day and a sol would again mess things up in short order.

This Islamic calendar is even worse. Not only is it *strictly* lunar, but the beginning of the month is determined *observationally*! The first day of the month is when you can see the barest sliver of the new moon right after sunset. Again, not easily transplanted.

All I'll say about the Baha'I calendar is that it consists of 19 months of 19 days, with 4 extra days at the end of the year to bring it up to 365. And yes a 5th extra day in leap years.

Now we come to the difference between the year (365.2425 days) and the etos (local solar year). This too is gonna throw things off religiously. And in other ways.