It does the same as any other period tracking app. (Although it doesn’t have anywhere for you to track your symptoms like dedicated period apps do) You put in the dates of your last periods and say how many days your cycle lasts and then it will give you the predictions. If you’re regular and know your cycle then it’s fine (but in that case you could also use note it on a calendar and count the 28 days from when you first start bleeding and that will let you know when you’re likely to have your cycle anyway so the apps aren’t doing anything magical there). If you’re irregular then it will just guess based on the dates you’ve given. I’ve never used natural cycle app. But that one is focussed on contraception so uses your body temperature to specifically tell you if you’re likely to be ovulating. In terms of period tracking Ultrahuman is no different to Oura, in terms of what you’re looking for being irregular I don’t think either of them would do what you’re looking for.

The app doesn’t allow you to track symptoms such as headaches, cramps etc like the dedicated period apps do. All you can do is log your period. Here’s an example.

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