Datetime does need to be part of the spec if you want your markup files portable otherwise every TOML parser might decode a date slightly differently. In that regard it is really no different to saying "01" (string) is different to 1 (integer) in terms of preserving your data's integrity.

I guess there's no way around that though, if you want dates to be first class members. Can't do "a bit of date".

We added a proper datetime type because the only thing worse than having one is not having one. If you had to supply a datetime as a string, every TOML file would have a different way of doing it, which is...not so obvious.

Excluding the datetime RFC in the name of minimalism would make the language much worse (coughjson). I feel like this is as simple as it could be, but no more.