V8 always assumes a UTC time zone when parsing ISO 8601 date strings with no time zone offset. QDateTime uses the local time zone if a trailing 'Z' or time zone offset is omitted. V8's behavior is deliberate and correct according to the ES5 errata (http://code.google.com/p/v8/issues/detail?id=1498).

There seems to be a question mark over the correctness of the ES5 errata which could see a future change in V8's behaviour, but for the sake of consistency in the mean time QML's parsing should probably try and match V8 as closely as possible.