private static string FormatW3COffset(TimeSpan offset, string separator) { var formattedOffset = String.Empty; if (offset >= TimeSpan.Zero) { formattedOffset = "+"; } return String.Concat( formattedOffset, offset.Hours.ToString("00", CultureInfo.InvariantCulture), separator, offset.Minutes.ToString("00", CultureInfo.InvariantCulture)); }