"Be conservative in what you do, be liberal in what you accept from others" they say. Also Z as a timezone designator is also widely used in iso 8601 timestamps. I believe the effort should be made to *parse* *any/all* of the ISO 8601 supported time-zone codes with one conversion, the list is not that long, just 'Z', HH, HH:MM, HHMM, longest match. Literal 'Z' really does not need to be supported for *output* at all, but for input, please.

Otherwise this will still go down the road of iso8601 library, which just tries to support all the YYmmddTHHMMSS.FFFFFFzzzz variants. It uses regular expressions to parse the dates as it is faster than trying N different formats with `strptime`