V4 Date.ParseString(): fix UTC-ness of date-only formats

ECMA-262 stipulates that date-only formats should be treated as UTC,
while date-times are handled as standard time, if no time zone is
explicitly given.  Tidied up the parser a bit in the process and
documented what the spec says.  Fixed some broken test-cases.

Handling of date-times without zone as local time is a correction
since edition 5.1 of ECMA-262 (which said to handle it as UTC):
http://www.ecma-international.org/ecma-262/7.0/index.html#sec-corrections-and-clarifications-in-ecmascript-2015-with-possible-compatibility-impact
We were previously handling both dates and date-times as local time,
violating the old spec for both and the revised spec for dates.

Task-number: QTBUG-56787
Change-Id: I557789d855b910ca6a859fca396af1a0205c9417
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

1 files changed, 2 insertions, 1 deletions

diff --git a/tests/auto/qml/qqmlqt/tst_qqmlqt.cpp b/tests/auto/qml/qqmlqt/tst_qqmlqt.cpp
index 0576650d01..6c920471c4 100644
--- a/tests/auto/qml/qqmlqt/tst_qqmlqt.cpp
+++ b/tests/auto/qml/qqmlqt/tst_qqmlqt.cpp
@@ -888,7 +888,8 @@ void tst_qqmlqt::dateTimeFormattingVariants_data()
     QTest::newRow("formatTime, qtime") << "formatTime" << QVariant::fromValue(time) << (QStringList() << temporary.time().toString(Qt::DefaultLocaleShortDate) << temporary.time().toString(Qt::DefaultLocaleLongDate) << temporary.time().toString("H:m:s a") << temporary.time().toString("hh:mm:ss.zzz"));
 
     QDate date(2011,5,31);
-    temporary = QDateTime(date);
+    // V4 reads the date in UTC but DateObject::toQDateTime() gives it back in local time:
+    temporary = QDateTime(date, QTime(0, 0, 0), Qt::UTC).toLocalTime();
     QTest::newRow("formatDate, qdate") << "formatDate" << QVariant::fromValue(date) << (QStringList() << temporary.date().toString(Qt::DefaultLocaleShortDate) << temporary.date().toString(Qt::DefaultLocaleLongDate) << temporary.date().toString("ddd MMMM d yy"));
     QTest::newRow("formatDateTime, qdate") << "formatDateTime" << QVariant::fromValue(date) << (QStringList() << temporary.toString(Qt::DefaultLocaleShortDate) << temporary.toString(Qt::DefaultLocaleLongDate) << temporary.toString("M/d/yy H:m:s a"));
     QTest::newRow("formatTime, qdate") << "formatTime" << QVariant::fromValue(date) << (QStringList() << temporary.time().toString(Qt::DefaultLocaleShortDate) << temporary.time().toString(Qt::DefaultLocaleLongDate) << temporary.time().toString("H:m:s a") << temporary.time().toString("hh:mm:ss.zzz"));