Allow space to seperate date and time

[flaviut]

The RFC cited allows applications to use along withT as the date-time separator:

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.

This would be a nice extension, and the RFC mentioning it creates precedent.

[mojombo]

Yes, that's true, but TOML craves simplicity, and I don't see a huge benefit to allowing the SPACE variant. Unless there are reasons I'm not seeing (and I don't think readability is one of them), I'd like to enforce the T format of RFC 3339.