Recently upgrade one application from .NET Core 3.1 to .NET 5. For some reason the DateTimeKind was Local in 3.1 and now it is UTC in .NET 5.
I created a simple project showing this problem,
https://github.com/ShehulCS/Dotnet5DateTimeIssue
Question,
The issue you're describing is related to a bug fix.
In short, the Z at the end of an ISO 8601 timestamp explicitly means UTC. The bug was that when such a value is obtained through model binding, it was previously being interpreted as DateTimeKind.Local instead of DateTimeKind.Utc. That bug has been corrected in 5.0.
The bug is described in this issue: https://github.com/dotnet/aspnetcore/issues/11584
It was fixed in this PR: https://github.com/dotnet/aspnetcore/pull/24893
A request to backport the fix to 3.1 was made (but denied) here: https://github.com/dotnet/aspnetcore/issues/27618
The new behavior is correct. If you were relying on the old behavior, you probably have other .NET code that needs to be corrected.
