How long can you stay? For the passport you actually hold.
You are in Thailand. Day 12 of 60. You must leave by 4 September.
That is the sentence the app exists to produce. It counts the days you have spent and the days you have left, against the rule that applies to your nationality — and if you hold two passports, it tells you which one to enter on. That is often the difference between ninety days and no limit at all.
Start a travel circle and you can see where the people you travel with are, and who has to leave first. Each phone publishes a name, a country, and that person's own count — never a location. The map pins a country, because a country is all the app is ever told.
There is no account, no analytics and no tracking. Your trips, your passports and your location stay on your device and in your own iCloud. There is no server for them to go to. A travel circle is an iCloud share between you and the people you invite; we cannot see it either.
An aid, not legal advice. Border authorities and official government sources are authoritative. Every rule in the app records where it came from and when it was read, says plainly when it has not been verified, and shows you both readings when its sources disagree. Verify before you travel.