The datetime type is still in development. It might work, but its behaviour is undefined until it’s officially released, and may change at any time without notice (or even stop working altogether). Because of that it’s generally not a good idea to use undocumented features.
We should finish it shortly, though, so stay tuned.
We were not planning to offer the date type at this time, nor any other type apart from those that are already available plus datetime. However, feel free to raise an appropriate feature request if you would like to see some other types, we will be happy to take it into account and possibly reevaluate our plans.