Why can't I use Date when querying in the swift client?

I'm trying to only fetch rows after a specific date. There is a URLQueryRepresentable protocol and most types have an extension for it, but there is none for Date.

I also couldn't find anything in the examples or documentation on how to transform a date so it conforms properly.

So

1. Why is there no extension for it, and
2. How should I convert the date to a string?