Board Thread:General Discussion/@comment-25980608-20201003034625/@comment-9605025-20201003041029

That URL has some unnecessary things if all you want it the registration time. Here is a shorter version. You can replace your username with anyone else's and get their registration time. You can also use "usids" instead of "ususers" in order to retrieve the data be user ID instead of by username. Also, you can search for multiple users at once by separating their names/IDs with "|".

That said, if you just want your own registration, you can also use this api endpoint instead. This one returns the information for whomever is requesting the data; no need to specify your own username. Also, this information is available on UCP wikis under the "User Profile" tab of Special:Preferences (but not on legacy wikis).