Is DateTimeOffset.UtcNow.DateTime equivalent to DateTime.UtcNow?

Question

I need to upgrade some piece of code from statically calling DateTime.UtcNow to calling a time provider service which returns, basically, DateTimeOffset.UtcNow. To further convert this DateTimeOffset instance to DateTime, there is the DateTime property. Alternatively, it seems that there is an implicit conversion from DateTimeOffset to DateTime.

I'm a bit concerned that there might be some edge cases that I can't see right now where these two would not be equivalent. Are there?

Answer 1

If you look at the value of DateTimeOffset.UtcNow.DateTime.Kind you will see the it is Unspecified. Unspecified kinds are treated as local times by the framework. The kind of DateTime.UtcNow is Utc, so there will be differences when timezone conversions are applied to and from the local timezone.

The work around is to use the DateTimeOffset.UtcNow.UtcDateTime which has the Utc kind specified.

Answer 2

Internally it looks like this:

  public static DateTimeOffset UtcNow {
        get { 
            return new DateTimeOffset(DateTime.UtcNow);
        } 
  } 

  public DateTime DateTime { 
        get {
            return ClockDateTime;
        }
    } 
   private DateTime ClockDateTime { 
        get {
            return new DateTime((m_dateTime + Offset).Ticks, DateTimeKind.Unspecified); 
        }
    }

  public DateTime UtcDateTime { 
        [Pure] 
        get {
            Contract.Ensures(Contract.Result<DateTime>().Kind == DateTimeKind.Utc); 
            return DateTime.SpecifyKind(m_dateTime, DateTimeKind.Utc);
        }
    }

So it looks like you could end up getting a DateTime that was based on UTC but then gets converted to Unspecified.