diff --git a/src/corelib/time/qdatetimeparser.cpp b/src/corelib/time/qdatetimeparser.cpp
index e5242b43eb..68ec73f471 100644
--- a/src/corelib/time/qdatetimeparser.cpp
+++ b/src/corelib/time/qdatetimeparser.cpp
@@ -1726,29 +1726,26 @@ QDateTimeParser::ParsedSection QDateTimeParser::findUtcOffset(QStringRef str) co
 QDateTimeParser::ParsedSection
 QDateTimeParser::findTimeZoneName(QStringRef str, const QDateTime &when) const
 {
-    int index = startsWithLocalTimeZone(str);
-    if (index > 0)  // won't actually use the offset, but need it to be valid
-        return ParsedSection(Acceptable, when.toLocalTime().offsetFromUtc(), index);
-
+    const int systemLength = startsWithLocalTimeZone(str);
 #if QT_CONFIG(timezone)
-    const int size = str.length();
-
     // Collect up plausibly-valid characters; let QTimeZone work out what's
     // truly valid.
-    for (; index < size; ++index) {
-        const QChar here = str[index];
-        if (here >= 127 || (!here.isLetterOrNumber() && !QLatin1String("/-_.+:").contains(here)))
-            break;
-    }
+    const auto invalidZoneNameCharacter = [] (const QChar &c) {
+        return c.unicode() >= 127u
+               || (!c.isLetterOrNumber() && !QLatin1String("+-./:_").contains(c));
+    };
+    int index = std::distance(str.cbegin(),
+                              std::find_if(str.cbegin(), str.cend(), invalidZoneNameCharacter));
 
-    while (index > 0) {
+    for (; index > systemLength; --index) {  // Find longest match
         str.truncate(index);
         QTimeZone zone(str.toLatin1());
         if (zone.isValid())
             return ParsedSection(Acceptable, zone.offsetFromUtc(when), index);
-        index--; // maybe we collected too much ...
     }
 #endif
+    if (systemLength > 0)  // won't actually use the offset, but need it to be valid
+        return ParsedSection(Acceptable, when.toLocalTime().offsetFromUtc(), systemLength);
     return ParsedSection();
 }
 
diff --git a/tests/auto/corelib/time/qdatetime/tst_qdatetime.cpp b/tests/auto/corelib/time/qdatetime/tst_qdatetime.cpp
index ccae0dc3c4..23a99e2f47 100644
--- a/tests/auto/corelib/time/qdatetime/tst_qdatetime.cpp
+++ b/tests/auto/corelib/time/qdatetime/tst_qdatetime.cpp
@@ -119,6 +119,8 @@ private slots:
     void fromStringDateFormat();
     void fromStringStringFormat_data();
     void fromStringStringFormat();
+    void fromStringStringFormat_localTimeZone_data();
+    void fromStringStringFormat_localTimeZone();
 #if defined(Q_OS_WIN) && QT_CONFIG(textdate)
     void fromString_LOCALE_ILDATE();
 #endif
@@ -2675,6 +2677,7 @@ void tst_QDateTime::fromStringStringFormat()
 
     QDateTime dt = QDateTime::fromString(string, format);
 
+    QCOMPARE(dt, expected);
     if (expected.isValid()) {
         QCOMPARE(dt.timeSpec(), expected.timeSpec());
 #if QT_CONFIG(timezone)
@@ -2684,7 +2687,42 @@ void tst_QDateTime::fromStringStringFormat()
         // OffsetFromUTC needs an offset check - we may as well do it for all:
         QCOMPARE(dt.offsetFromUtc(), expected.offsetFromUtc());
     }
-    QCOMPARE(dt, expected);
+}
+
+void tst_QDateTime::fromStringStringFormat_localTimeZone_data()
+{
+    QTest::addColumn<QByteArray>("localTimeZone");
+    QTest::addColumn<QString>("string");
+    QTest::addColumn<QString>("format");
+    QTest::addColumn<QDateTime>("expected");
+
+#if QT_CONFIG(timezone)
+    QTimeZone etcGmtWithOffset("Etc/GMT+3");
+    if (etcGmtWithOffset.isValid()) {
+        QTest::newRow("local-timezone-with-offset:Etc/GMT+3") << QByteArrayLiteral("GMT")
+            << QString("2008-10-13 Etc/GMT+3 11.50") << QString("yyyy-MM-dd t hh.mm")
+            << QDateTime(QDate(2008, 10, 13), QTime(11, 50), etcGmtWithOffset);
+    }
+    QTimeZone gmtWithOffset("GMT-2");
+    if (gmtWithOffset.isValid()) {
+        QTest::newRow("local-timezone-with-offset:GMT-2") << QByteArrayLiteral("GMT")
+            << QString("2008-10-13 GMT-2 11.50") << QString("yyyy-MM-dd t hh.mm")
+            << QDateTime(QDate(2008, 10, 13), QTime(11, 50), gmtWithOffset);
+    }
+    QTimeZone gmt("GMT");
+    if (gmt.isValid()) {
+        QTest::newRow("local-timezone-with-offset:GMT") << QByteArrayLiteral("GMT")
+            << QString("2008-10-13 GMT 11.50") << QString("yyyy-MM-dd t hh.mm")
+            << QDateTime(QDate(2008, 10, 13), QTime(11, 50), gmt);
+    }
+#endif
+}
+
+void tst_QDateTime::fromStringStringFormat_localTimeZone()
+{
+    QFETCH(QByteArray, localTimeZone);
+    TimeZoneRollback useZone(localTimeZone);  // enforce test's time zone
+    fromStringStringFormat();  // call basic fromStringStringFormat test
 }
 
 #if defined(Q_OS_WIN) && QT_CONFIG(textdate)