Clarification on ISO 8601 DateTimes

I am scratching my head over the wording of this instruction in the API docs for Call Logs.

The end datetime for resulting records in (ISO 8601)[https://en.wikipedia.org/wiki/ISO_8601] format including timezone, for example 2016-03-10T18:07:52.534Z

What does it mean, "including timezone" ?? I am using the C# SDK and this is confusing to me.

Are we supposed to include the timezone offset? (-04:00)

If that's the case, the provided example isnt helpful at all