If you add a date/time field to a content type and have it use the "Select List" formatter, then every input in the Page Data form will become very slow to respond. It will be quite possible to type a dozen characters into an input before what you've typed is visible in the input.
It is possible this will be indirectly fixed by addressing this issue: 📌 Validation for fields with default datelist widget Active but this is ugly enough that the situation should be monitored in a dedicated issue as well.
Active
0.0
Redux-integrated field widgets
