Hi ​@Clara,

if you can't change the date in the app, try via the Strava website: https://www.strava.com/settings/profile

If you’ve changed your birth date recently, you might need to wait (maybe even several days) till you can change it again. It appears that there's a limit on how often users can change this, probably to prevent cheating.

If you still can't do the change yourself even after several days, you'll need to contact Strava Support - as this is a community hub, i.e. fellow athletes advising each other, but without any access to people's accounts. Here's how: https://support.strava.com/hc/en-us/articles/216917777-How-Do-I-Contact-Strava-Support