[adityapurwa]

If granular accuracy is not an important factor, you can also use Islamic calendar to calculate the moon phase. Muslims uses lunar cycles for some religious events (e.g. the Ayyamul Bidh or 3 days fasting during full moon). So when its 15 of an Islamic calendar, it’ll be a full moon.

I used this approach because most platforms supports islamic calendar.

I really like the offline first approach, and would definitely use the library when there’s a need.

Thanks for sharing!

[throwup238]

I wonder, how is Allah's tolerance towards technotheological errors?

What if there's a bug in the calendar for Ramadan or Salah?

[adityapurwa]

In Islam, err is forgiven. If you’ve done your best and there’s a bug you missed, then its forgiven, and when you discover it, just fix it.

That’s why if a scholar based with intensive research and data, has concluded that X is true. If in the end its really true, they’ll receive two rewards; when its debunked and it was actually false, they receive one reward. The sin is to be ignorant and without any research and data concluded that X is true.

Specifically for Ramadan, the guideline is to use Moon sighting. If you see a new moon, then you begin fasting. If not, then you postpone for a day before starting Ramadan. Usually there’s a committee that does this and they will announce the result. But it doesn’t prevent anyone with the ability to observe to decide when to start Ramadan.

Salah guideline is the sun, e.g the dawn prayer is when there’s thin strike of the sun on the horizon. So to calculate the prayer time you use the sun position relative to your position on earth. If there’s a bug that somehow err the prayer time to ~5 minutes. We can always observe the sun first.

So there’s always this second factor that you can use to validate the first method. Time seems off? Look at the sun. Sun not visible? Estimate with time. Both seems off? Estimate with the variables that you can observe.

“ God does not burden any soul with more than it can bear “ (Al Baqarah 286)

——- So to answer the question, the tolerance depends on your effort on trying to reduce the err.

God knows best

[httgp]

Really cool, thank you!