I had a similar problem with the JSON serializer, I could solve it by using:
var myDate = new DateTime(2019, 1, 1, 12, 0, 0, DateTimeKind.Local);
If you don't want the trailing Timezone information, use:
var myDate = new DateTime(2019, 1, 1, 12, 0, 0, DateTimeKind.Unspecified);
Also see:
DateTimeKind Enum (System) | Microsoft Docs[
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