Comment by chuckadams

You're absolutely right, I confused it with RFC3339. ISO8601 suggests that the 'T' is optional, but only in the sense of leaving it out... and fails to provide any actual examples of doing so.

The amount of handwaving in ISO8601 could turn a windmill, though in this respect RFC3339 is not much better. The ABNF clearly shows "T" (case-insensitive) as the only separator, but immediately afterward gives us this:

> NOTE: ISO 8601 defines date and time separated by "T". Applications using this syntax may choose, for the sake of readability, to specify a full-date and full-time separated by (say) a space character.

Separated by (say) whatever the hell you want apparently. I'm getting bruises on my face from all the palming.