jkingwebYes, I'm currently testing all the expected input formats. The aforementioned ambiguities relate to output formats, since "HH" and "XX" (hours in times and zones, respectively) don't differentiate between output with and without leading zero. It's also unclear when implementations may or may not or must or must not output "Z" as the time zone, making testing UTC+0 times more difficult.
[tantek]yes, feel free to add more test cases as comments on that issue, that way it will be easier to see how they all relate and I can come up with rational methods of handling them