Some of my tests require that I need to test the date time results (like time stamps etc.). In order to be able to test the date time string I created a simple DateTime abstraction that I'm going to use in other projects later. It should replace direct calls to DateTime.(Utc)Now. Or should I rather call it TestValue instead of ConstValue?

public abstract class DateTimeProvider
{
    public abstract DateTime Value { get; }

    public DateTime? ConstValue { get; set; }       

    public static implicit operator DateTime(DateTimeProvider dateTimeProvider)
    {
        return dateTimeProvider.Value;
    }
}

public class NowDateTimeProvider : DateTimeProvider
{
    public override DateTime Value
    {
        get { return ConstValue ?? DateTime.Now; }
    }
}

public class UtcNowDateTimeProvider : DateTimeProvider
{
    public override DateTime Value
    {
        get { return ConstValue ?? DateTime.UtcNow; }
    }
}