DateTime.ParseExact(s, "yyyyMMddTHHmmss+zzzz", CultureInfo.InvariantCulture);

using System;
using System.Globalization;

class Test
{
    static void Main()
    {
        string text = "20100804T104413+0100";

        DateTime dt = DateTime.ParseExact
            (text,
             "yyyyMMdd'T'HHmmsszzz",
             CultureInfo.InvariantCulture);
        Console.WriteLine(dt);
    }
}

// DON'T DO THIS, dangerous code ahead:

DateTime time = DateTime.ParseExact(
     "20100804T104413+0100",
     "yyyyMMdd'T'HHmmssK",
     CultureInfo.InvariantCulture,
     DateTimeStyles.RoundtripKind);

// loosing data when converting back:
string convertedBack = time.ToString("yyyyMMdd'T'HHmmssK");
// convertedBack now contains "20100804T114413+02:00"

// DO THIS instead:

DateTimeOffset parsedDate = DateTimeOffset.ParseExact(
     "20100804T104413+0100",
     "yyyyMMdd'T'HHmmsszzz",
     CultureInfo.InvariantCulture,
     DateTimeStyles.RoundtripKind);

// converting back is now easy:
convertedBack = parsedDate.ToString("yyyyMMdd'T'HHmmssK");
// convertedBack contains the string "20100804T104413+01:00"

if (offset >= TimeSpan.Zero)
{
    result.Append('+');
}
else
{
    result.Append('-');
    offset = offset.Negate();
}
result.AppendFormat(CultureInfo.InvariantCulture, "{0:00}:{1:00}", new object[] { offset.Hours, offset.Minutes });

convertedBack = parsedDate.ToString("yyyyMMdd'T'HHmmssK").Replace(":", "");

moment("20150107T085108+0100", 'YYYYMMDDTHHmmssZ').format('YYYY-MM-DD HH:mm:ss')