Description

In .NET 11 Preview 1, the behavior of TimeZoneInfo.GetUtcOffset appears to have changed when called with an invalid DateTime. I would like to know whether this change is intentional or a regression.

For example, Paraguay used UTC-4 before switching permanently to UTC-3. In its TimeZoneInfo.GetAdjustmentRules(), all the rules contain BaseUtcOffsetDelta == -01:00.

In .NET 10, calling GetUtcOffset(new DateTime(2023, 10, 6, 0, 0, 0)) (the specified time here is invalid), returned the standard time offset for that year, which is -04:00. That means the BaseUtcOffsetDelta was taken into account.

However, in .NET 11 Preview 1, the same call returns -03:00, which corresponds to the current BaseUtcOffset without applying BaseUtcOffsetDelta for the year of 2023.

Could you confirm whether this small behavioral change is expected?

Reproduction Steps

using System;

public class Program {
    public static void Main() {
        var paraguayTimeZone = TimeZoneInfo.FindSystemTimeZoneById("Paraguay Standard Time");
        var invalidDateTime = new DateTime(2023, 10, 6, 0, 0, 0);

        var utcOffset = paraguayTimeZone.GetUtcOffset(invalidDateTime);
        Console.WriteLine($"UtcOffset: {utcOffset}");
    }
}

Expected behavior

Base offset for the year of 2023 is printed (.NET 10 behavior):

UtcOffset: -04:00:00

Actual behavior

Current base offset is printed (.NET 11 behavior):

UtcOffset: -03:00:00

Regression?

No response

Known Workarounds

No response

Configuration

OS: Windows 11
.NET version: .NET 11 Preview 1

Other information

No response