Changing to a format string that is compatible with parse operations in Mono

[StanleyGoldman]

In recently merged pull request #457, we used the format string o to format DateTimeOffset objects to the Iso8601 format.

Although this works for output, it does not work for parsing. Usingn o in DateTimeOffset.Parse() or DateTimeOffset.ParseExact() throws an exception with Invalid Format String as the message.

Using the format string yyyy-MM-ddTHH\\:mm\\:ss.fffffffzzz outputs the same content as o, but also has the added benefit of working in Mono/Unity.

[drguthals]

Looks good!

[grokys]

What do you mean by:

Although this works for output, it does not work for parsing.

What doesn't work for parsing? You can't parse ISO8601 format dates on mono?

[StanleyGoldman]

I never heard of the DateTimeOffset format string o until recently.
When I use that same format string in DateTimeOffset.Parse() or DateTimeOffset.ParseExact() I get an Invalid Format String error.

I'll update the body above to be clearer...