I recorded last nights ride with strava.
Tried to upload it and my phone failed to sync, as it often does, but I exported the gpx and manually uploaded it.
Noticed today that it wasn’t appearing on my dashboard, but was recorded in my activities. Investigating, it was logged as Feb 8th.

So I checked out the gpx file. The timestamps are all over the place, randomly advancing in time and dates. I edited the file to change the date to yesterday, but the time is still wrong. Weirdly it does give the correct total moving and recorded time.

So, is it something wrong with my phone, or with the strava app?

I get that if I set off before the GPS has synced properly (and so got the right time). I use a computer though, not a phone (if that matters). If you email Strava they will sort it out for you pretty quickly