>Great. I just cobbled things together as a 'proof of concept' (except all it did at first was prove that it didn't work :-{ )

Succeeded anyway

>Now it looks good enough for production code!
>Next useful thing would be extension methods for DateTime to add and subtract DateTimeSpan....
>

Mods
(1) Changed property MilliSeconds to Milliseconds and _MilliSeconds to Milliseconds - more in line with the Milliseconds of DateTime

(2) Added a constructor that accepts DateTimeOffset

		public DateTimeSpan(DateTimeOffset start, DateTimeOffset end)
			: this(start.UtcDateTime, end.UtcDateTime)
		{
		}

(3) Extension methods Add and Subtract for DateTime and DateTimeOffset

	public static partial class ExtensionMethods_DateTime
	{
		//______________________________________________________________________
		public static DateTime Add(this DateTime dt, DateTimeSpan dts)
		{
			return dt.AddYears(dts.Years)
				.AddMonths(dts.Months)
				.AddDays(dts.Days)
				.AddHours(dts.Hours)
				.AddMinutes(dts.Minutes)
				.AddSeconds(dts.Seconds)
				.AddMilliseconds(dts.Milliseconds);
		}
		//______________________________________________________________________
		public static DateTime Subtract(this DateTime dt, DateTimeSpan dts)
		{
			return dt.AddYears(-dts.Years)
				.AddMonths(-dts.Months)
				.AddDays(-dts.Days)
				.AddHours(-dts.Hours)
				.AddMinutes(-dts.Minutes)
				.AddSeconds(-dts.Seconds)
				.AddMilliseconds(-dts.Milliseconds);
		}
		//______________________________________________________________________
	
	}

	public static partial class ExtensionMethods_DateTimeOffset
	{
		//______________________________________________________________________
		public static DateTimeOffset Add(this DateTimeOffset dto, DateTimeSpan dts)
		{
			return dto.AddYears(dts.Years)
				.AddMonths(dts.Months)
				.AddDays(dts.Days)
				.AddHours(dts.Hours)
				.AddMinutes(dts.Minutes)
				.AddSeconds(dts.Seconds)
				.AddMilliseconds(dts.Milliseconds);
		}
		//______________________________________________________________________
		public static DateTimeOffset Subtract(this DateTimeOffset dto, DateTimeSpan dts)
		{
			return dto.AddYears(-dts.Years)
				.AddMonths(-dts.Months)
				.AddDays(-dts.Days)
				.AddHours(-dts.Hours)
				.AddMinutes(-dts.Minutes)
				.AddSeconds(-dts.Seconds)
				.AddMilliseconds(-dts.Milliseconds);
		}
		//______________________________________________________________________
	
	}