How to control appearance of ':' in time zone offset when parsing/formatting Datetime

I'm working with a protocol that may optionally include a time zone offset when specifying datetime information. My code is written in C# and we are using the 4.0 .NET runtime. I see that there is a formatting option "zzz" for including timezone information when parsing and formatting, however, it appears that the colon (:) is fixed. For instance, a Datetime formatted with the custom format string (yyyyMMddHHmmsszzz) might appear as:

20100309101530-05:00

The protocol I am working with does not include the colon in the timezone offset. This protocol will format datetimes, and expect them to be formatted as:

20100309101530-0500

Is there a way to control the appearance of the colon when parsing or formatting datetime with a custom formatter that includes the timezone offset?

Doesn't look like there is anything built-in (you can use zz, but that leaves out the minutes).

You can roll your own by instantiating a DateTimeFormatInfo, setting TimeSeparator to string.Empty and using that as the IFormatProvider when calling DateTime.ToString (and make the call explicit, if it is not already).

But frankly, using Replace to remove the unwanted : from the default return value is so much easier.

I faced the same problem, ended up using an extension

    public static class DateTimeExtensions
    {        
        public static String ToSomeFormat(this DateTimeOffset dateTime)
        {
            return dateTime.ToString("yyyyMMddHHmmsszzz").Replace(":", "");
        }
    }

If you're using it in a place where it doesn't make sense to use replace or extend (for example something that might want to output as -05:00 with a colon when passed as zzz) and the minutes don't matter you could fake it with zz00.

var date = new DateTimeOffset(2008, 8, 1, 0, 0, 0, new TimeSpan(-5, 0, 0));
Console.WriteLine(date.ToString("yyyy-MM-dd-HH:mm:ss(zz00)"));
// outputs 2008-08-01-00:00:00(-0500)