Excel stores time values as
Date[
^] (
DateTime[
^] in C#). See here:
Data types in Data Models (Excel)[
^]
I think you need to format date as "time":
Custom Date and Time Format Strings[
^],
String Format For DateTime (C#)[
^]
DateTime date1 = new DateTime(2013, 4, 24, 19, 27, 15, 18);
CultureInfo ci = CultureInfo.InvariantCulture;
Console.WriteLine(date1.ToString("hh:mm:ss.f", ci));
Console.WriteLine(date1.ToString("hh:mm:ss.F", ci));