Linq Select DateTime returns local time

[f1nzer]

class Data 
{ 
   public DateTime Date { get; set; }
}

Query: session.Query<Data>().ToList() returns data with DateTime in UTC format.
Query: session.Query<Data>().Select(x => new { x.DateTime }).ToList() returns data in local format.

DateTime is indexed via duplicated field and DuplicatedFieldUseTimestampWithoutTimeZoneForDateTime = false

[oskardudycz]

@f1nzer could you check https://www.npgsql.org/doc/types/datetime.html? It seems to be that it looks like default Npgsql behaviour. See also more in: #1179

[tetious]

Are you saying it is converting the date to the local timezone in the second case? That might indeed be a bug.

I'd expect the DateTime Kind set to Unspecified in both cases if I'm understanding the mapping documentation in the npgsql docs. Unspecified can make conversions a bit surprising if you don't understand how it influences them.

If Kind == Unspecified and you call ToUniversalTime, you will get a DateTime converted as if the source was in the local timezone. If you call ToLocalTime, you will get a DateTime converted as if the source was in UTC.

In other words, either conversion method will always result in a converted value when Kind is Unspecified, which is probably not what you want in this case.

When you know the source is in UTC, you can make ToUniversalTime "safe" by calling DateTime.SpecifyKind to set Kind to Utc.