I just wanted to post this here as general FYI/lifehack, if it’s not helpful to you, just leave it. It might be helpful for some people though especially if you live in an area where the adhan AKA muslim call to prayer is broadcast (I know it really cleared things up for me A LOT). Also: you could definitely just do the same calculation yourself without it belonging to any religion.
In MN39, the Buddha instructs monastics to meditate in the first and last watches of the night. This has since gone on to become a source of great confusion, as the manner of calculating the watches has not been fully transmitted.
I know the broadcasting of the adhan (muslim call to prayer) is a controversial topic, which isn’t what I want to discuss. However, it is related to our system because the call to prayer is conveniently also calculated according to the three watches of the night.
(Some people believe than many of the published adhan times are actually off (too early in the morning) by up to 10 minutes- as this is a specialist topic, I don’t want to go into it, but it might be worthwhile keeping in mind.)
Also, this is just generic, I am sure there are different Islamic schools which have actual experts in this topic.
Anyway, from what I have researched, to calculate the watches of the night Islamically:
- Take time from sunset-sunrise and divide by three (works out at about 3hrs each watch at the moment).
- The time for sleeping is normally the latter part of the first watch of the night. Take the first watch of the night and divide by two (about 1.5hrs right now) to get the beginning of the latter part of the first watch. This is isha prayer time- the time for sleeping is after that for Muslims.
- Do the same thing with the last watch of the night . Subtract approx 3hrs from sunrise as per 1., and divide by two again to get the first part of the last watch of the night. I.e. Muslims would rise before this time for fajr prayer.
Tada! Watches of the night solved!
Now someone just needs to make a Buddhist clock app.