we are using Dynamics 365 ONPREM ( and it seems that DateTime fields on Unified Interface app forms can't handle Central European Summertime.
However this work's fine in Unified Interface views, and everywhere in apps that uses the classic Web UI.

This issue only manifests in Internet Explorer 11.

As you can see from the image, the right side is (Chrome), left is (IE 11).

The Registered date is Winter Time (CET), and Avregistrerad den is (CEST "Summer time").
CEST shows just fine in Chrome but in IE it's a 1 hour diff on the same record.