Sorry, it is a bug. We are working on the fix of handling datetime and guid literals in REST API v.2.
In general, the fix is ready in the 10.2.600 and 10.2.500 development branches.
Because of the New Year holidays the fix in 10.2.500 will be released in January.
Anyway, the following format - http://localhost:1234/api/values/1?date=2017-04-17T05:45:18.070Z is correct.