DateString["ISODateTime"]
(* "2017-04-28T11:45:14" *)

DateObject["2017-04-28T11:45:14"]
(* DateObject[{2017, 4, 28, 11, 45, 14}, "Instant", "Gregorian", -4.] *)

isoDateString = "2017-04-28T01:50:52.000Z";

DateObject[isoDateString]
(* DateObject[{2017, 4, 28, 1, 50, 52.}, "Instant", "Gregorian", -4.] *)

isoDateString = "2017-04-28T01:50:52.000Z";

TimeZoneConvert @ Block[{$TimeZone = 0}, DateObject @ isoDateString]