JSON doesn't have datatypes for either date or time. Both are represented as strings. Server and client must ensure that date/time strings are in ISO 8601 format. E.g.:
2015-04-19T11:08:53Z 2015-04-10T11:08 2015-04-19
Developers should not assume that the server is in the same time zone as the browser. All timezone-aware expressions should contain time zone offset or "Z" suffix (for "Zulu" time).