Hi Peter,
Greetings from Syncfusion Support.
Since by default, Blazor client side application considers UTC as timezone, the reported problem “appointments duration changed to UTC while editing or creating appointments” occurs in all client-side applications whereas server side application will works properly considering system timezone.
As our sample browser is client-side application, the issue reproduces in the Sample Browser samples. We have already planned to fix the issue “client-side application not considering system timezone” in our source which can be tracked from the following link and the fix will be included in our Volume 3 SP1, 2019 release.
We would appreciate your patience until then.
Regards,
Nevitha.