The app's city menu

Indian almanacs do not start the day at midnight. They start it at sunrise. Sunrise is not one time for everybody. Every place on earth gets its own.

That matters because of lunar days. A lunar day is called a tithi. It is one step in the moon's separation from the sun, and lasts a little under 24 hours, so it never fits inside one of our dates. It may start on Tuesday afternoon and end on Wednesday evening.

So the almanac needs a rule for which date carries its name. The rule is one minute long: whichever tithi is running at sunrise names the whole day.

Now put the two together. The city in your app chooses a sunrise. The sunrise chooses the name. The name is the date printed for your fast or your festival.

Here is the case that fools people. Delhi is about 22 degrees of longitude east of Dubai. The earth turns 15 degrees an hour, so Delhi's sun does everything about 88 minutes earlier. Indian clocks also run 90 minutes ahead of Gulf clocks. The two almost cancel out, and the sheets print sunrise within about 10 minutes of each other all year. A wrong setting looks right.

It is still wrong. The app is reading the sky an hour and a half too early. A tithi averages about twenty-three and a half hours, and an hour and a half is roughly a sixteenth of that. So now and then your phone gives a different date from the temple down the road.

The wrong city gets there in one of two ways. Either nobody ever changed the app's default, or it was set years ago and life moved on: a house move, a phone restored from a backup, a relative who installed it while visiting.

The check takes two minutes. Find the field. See whether it holds a fixed city or your live location. Check which clock the times are printed in. Compare its sunrise against a free official table for your town. Then compare one date you care about with your temple's list.