diff --git a/src/corelib/io/qlockfile.h b/src/corelib/io/qlockfile.h
index aa5ad5e772f..ad58ba727d4 100644
--- a/src/corelib/io/qlockfile.h
+++ b/src/corelib/io/qlockfile.h
@@ -43,9 +43,7 @@
 #include <QtCore/qstring.h>
 #include <QtCore/qscopedpointer.h>
 
-#if __has_include(<chrono>)
-#    include <chrono>
-#endif
+#include <chrono>
 
 QT_BEGIN_NAMESPACE
 
@@ -66,7 +64,6 @@ public:
     void setStaleLockTime(int);
     int staleLockTime() const;
 
-#if __has_include(<chrono>)
     bool tryLock(std::chrono::milliseconds timeout) { return tryLock(int(timeout.count())); }
 
     void setStaleLockTime(std::chrono::milliseconds value) { setStaleLockTime(int(value.count())); }
@@ -75,7 +72,6 @@ public:
     {
         return std::chrono::milliseconds(staleLockTime());
     }
-#endif
 
     bool isLocked() const;
     bool getLockInfo(qint64 *pid, QString *hostname, QString *appname) const;
diff --git a/src/corelib/kernel/qdeadlinetimer.h b/src/corelib/kernel/qdeadlinetimer.h
index 6bc64345515..eec4cea3cee 100644
--- a/src/corelib/kernel/qdeadlinetimer.h
+++ b/src/corelib/kernel/qdeadlinetimer.h
@@ -52,9 +52,7 @@
 
 #include <limits>
 
-#if __has_include(<chrono>)
-#  include <chrono>
-#endif
+#include <chrono>
 
 QT_BEGIN_NAMESPACE
 
@@ -120,7 +118,6 @@ public:
     QDeadlineTimer &operator-=(qint64 msecs)
     { *this = *this + (-msecs); return *this; }
 
-#if __has_include(<chrono>) || defined(Q_CLANG_QDOC)
     template <class Clock, class Duration>
     QDeadlineTimer(std::chrono::time_point<Clock, Duration> deadline_,
                    Qt::TimerType type_ = Qt::CoarseTimer) : t2(0)
@@ -178,7 +175,6 @@ public:
     template <class Rep, class Period>
     friend QDeadlineTimer operator+=(QDeadlineTimer &dt, std::chrono::duration<Rep, Period> value)
     { return dt = dt + value; }
-#endif
 
 private:
     qint64 t1;
@@ -192,7 +188,7 @@ public:
     QPair<qint64, unsigned> _q_data() const { return qMakePair(t1, t2); }
 };
 
-#if __has_include(<chrono>) && (defined(Q_OS_DARWIN) || defined(Q_OS_LINUX) || (defined(Q_CC_MSVC) && Q_CC_MSVC >= 1900))
+#if defined(Q_OS_DARWIN) || defined(Q_OS_LINUX) || (defined(Q_CC_MSVC) && Q_CC_MSVC >= 1900)
 // We know for these OS/compilers that the std::chrono::steady_clock uses the same
 // reference time as QDeadlineTimer
 
diff --git a/src/corelib/kernel/qobject.h b/src/corelib/kernel/qobject.h
index 8a45e73b0e9..7725ad076b1 100644
--- a/src/corelib/kernel/qobject.h
+++ b/src/corelib/kernel/qobject.h
@@ -56,9 +56,7 @@
 #include <QtCore/qobject_impl.h>
 #include <QtCore/qbindingstorage.h>
 
-#if __has_include(<chrono>)
-#  include <chrono>
-#endif
+#include <chrono>
 
 QT_BEGIN_NAMESPACE
 
@@ -155,13 +153,11 @@ public:
     void moveToThread(QThread *thread);
 
     int startTimer(int interval, Qt::TimerType timerType = Qt::CoarseTimer);
-#if __has_include(<chrono>)
     Q_ALWAYS_INLINE
     int startTimer(std::chrono::milliseconds time, Qt::TimerType timerType = Qt::CoarseTimer)
     {
         return startTimer(int(time.count()), timerType);
     }
-#endif
     void killTimer(int id);
 
     template<typename T>
diff --git a/src/corelib/kernel/qtimer.h b/src/corelib/kernel/qtimer.h
index 2b262f63114..7e6404b2c54 100644
--- a/src/corelib/kernel/qtimer.h
+++ b/src/corelib/kernel/qtimer.h
@@ -47,9 +47,7 @@
 #include <QtCore/qbasictimer.h> // conceptual inheritance
 #include <QtCore/qobject.h>
 
-#if __has_include(<chrono>)
-#  include <chrono>
-#endif
+#include <chrono>
 
 QT_BEGIN_NAMESPACE
 
@@ -181,7 +179,6 @@ Q_SIGNALS:
     void timeout(QPrivateSignal);
 
 public:
-#if __has_include(<chrono>) || defined(Q_QDOC)
     void setInterval(std::chrono::milliseconds value)
     {
         setInterval(int(value.count()));
@@ -211,7 +208,6 @@ public:
     {
         start(int(value.count()));
     }
-#endif
 
 protected:
     void timerEvent(QTimerEvent *) override;
@@ -228,7 +224,6 @@ private:
     static void singleShotImpl(int msec, Qt::TimerType timerType,
                                const QObject *receiver, QtPrivate::QSlotObjectBase *slotObj);
 
-#if __has_include(<chrono>)
     static Qt::TimerType defaultTypeFor(std::chrono::milliseconds interval)
     { return defaultTypeFor(int(interval.count())); }
 
@@ -238,7 +233,6 @@ private:
         singleShotImpl(int(interval.count()),
                        timerType, receiver, slotObj);
     }
-#endif
 };
 
 QT_END_NAMESPACE
diff --git a/src/corelib/thread/qmutex.h b/src/corelib/thread/qmutex.h
index 19463da6198..7f3e4148cb5 100644
--- a/src/corelib/thread/qmutex.h
+++ b/src/corelib/thread/qmutex.h
@@ -44,10 +44,8 @@
 #include <QtCore/qatomic.h>
 #include <new>
 
-#if __has_include(<chrono>)
-#  include <chrono>
-#  include <limits>
-#endif
+#include <chrono>
+#include <limits>
 
 class tst_QMutex;
 
@@ -66,7 +64,6 @@ class QMutex;
 class QRecursiveMutex;
 class QMutexPrivate;
 
-#if __has_include(<chrono>)
 namespace QtPrivate
 {
     template<class Rep, class Period>
@@ -92,7 +89,6 @@ namespace QtPrivate
         return ms < maxInt ? int(ms) : maxInt;
     }
 }
-#endif
 
 class Q_CORE_EXPORT QBasicMutex
 {
diff --git a/tests/auto/corelib/kernel/qdeadlinetimer/tst_qdeadlinetimer.cpp b/tests/auto/corelib/kernel/qdeadlinetimer/tst_qdeadlinetimer.cpp
index 540856ad6e6..87ab016fe66 100644
--- a/tests/auto/corelib/kernel/qdeadlinetimer/tst_qdeadlinetimer.cpp
+++ b/tests/auto/corelib/kernel/qdeadlinetimer/tst_qdeadlinetimer.cpp
@@ -33,9 +33,7 @@
 #include <QTest>
 #include <QTimer>
 
-#if __has_include(<chrono>)
-#  include <chrono>
-#endif
+#include <chrono>
 
 static const int minResolution = 400; // the minimum resolution for the tests
 
@@ -520,9 +518,6 @@ void tst_QDeadlineTimer::expire()
 
 void tst_QDeadlineTimer::stdchrono()
 {
-#if !__has_include(<chrono>)
-    QSKIP("std::chrono not found on this system");
-#else
     using namespace std::chrono;
     QFETCH_GLOBAL(Qt::TimerType, timerType);
 
@@ -722,7 +717,6 @@ void tst_QDeadlineTimer::stdchrono()
     QVERIFY(deadline.deadline<steady_clock>() <= (steady_clock::now() + seconds(1) + milliseconds(minResolution)));
     QVERIFY(deadline.deadline<system_clock>() > (system_clock::now() + seconds(1) - milliseconds(minResolution)));
     QVERIFY(deadline.deadline<system_clock>() <= (system_clock::now() + seconds(1) + milliseconds(minResolution)));
-#endif
 }
 
 QTEST_MAIN(tst_QDeadlineTimer)
diff --git a/tests/auto/corelib/kernel/qtimer/tst_qtimer.cpp b/tests/auto/corelib/kernel/qtimer/tst_qtimer.cpp
index b3a500fbd87..6cc9dd92207 100644
--- a/tests/auto/corelib/kernel/qtimer/tst_qtimer.cpp
+++ b/tests/auto/corelib/kernel/qtimer/tst_qtimer.cpp
@@ -265,19 +265,14 @@ void tst_QTimer::remainingTimeDuringActivation()
 
 namespace {
 
-#if __has_include(<chrono>)
     template <typename T>
     std::chrono::milliseconds to_ms(T t)
     { return std::chrono::duration_cast<std::chrono::milliseconds>(t); }
-#endif
 
 } // unnamed namespace
 
 void tst_QTimer::basic_chrono()
 {
-#if !__has_include(<chrono>)
-    QSKIP("This test requires C++11 <chrono> support");
-#else
     // duplicates zeroTimer, singleShotTimeout, interval and remainingTime
     using namespace std::chrono;
     QTimer timer;
@@ -318,7 +313,6 @@ void tst_QTimer::basic_chrono()
     QCOMPARE(timeoutSpy.count(), 1);
     QTest::qWait(500);
     QCOMPARE(timeoutSpy.count(), 1);
-#endif
 }
 
 void tst_QTimer::livelock_data()
@@ -915,9 +909,6 @@ void tst_QTimer::singleShotToFunctors()
 
 void tst_QTimer::singleShot_chrono()
 {
-#if !__has_include(<chrono>)
-    QSKIP("This test requires C++11 <chrono> support");
-#else
     // duplicates singleShotStaticFunctionZeroTimeout and singleShotToFunctors
     using namespace std::chrono;
     {
@@ -954,7 +945,6 @@ void tst_QTimer::singleShot_chrono()
     QTRY_COMPARE(count, 3);
 
     _e.reset();
-#endif
 }
 
 class DontBlockEvents : public QObject
diff --git a/tests/auto/corelib/thread/qmutex/tst_qmutex.cpp b/tests/auto/corelib/thread/qmutex/tst_qmutex.cpp
index c00ddea9085..36a7cec3990 100644
--- a/tests/auto/corelib/thread/qmutex/tst_qmutex.cpp
+++ b/tests/auto/corelib/thread/qmutex/tst_qmutex.cpp
@@ -91,9 +91,7 @@ enum {
     waitTime = 100
 };
 
-#if __has_include(<chrono>)
 static constexpr std::chrono::milliseconds waitTimeAsDuration(waitTime);
-#endif
 
 void tst_QMutex::convertToMilliseconds_data()
 {
@@ -102,10 +100,6 @@ void tst_QMutex::convertToMilliseconds_data()
     QTest::addColumn<qint64>("intValue");
     QTest::addColumn<qint64>("expected");
 
-#if !__has_include(<chrono>)
-    QSKIP("This test requires <chrono>");
-#endif
-
     auto add = [](TimeUnit unit, double d, long long i, qint64 expected) {
         const QScopedArrayPointer<char> enumName(QTest::toString(unit));
         QTest::addRow("%s:%f:%lld", enumName.data(), d, i)
@@ -158,9 +152,6 @@ void tst_QMutex::convertToMilliseconds_data()
 
 void tst_QMutex::convertToMilliseconds()
 {
-#if !__has_include(<chrono>)
-    QSKIP("This test requires <chrono>");
-#else
     QFETCH(TimeUnit, unit);
     QFETCH(double, doubleValue);
     QFETCH(qint64, intValue);
@@ -198,7 +189,6 @@ void tst_QMutex::convertToMilliseconds()
 #undef DO
 #undef CASE
     }
-#endif
 }
 
 void tst_QMutex::tryLock_non_recursive()
@@ -326,10 +316,8 @@ void tst_QMutex::tryLock_non_recursive()
     thread.wait();
 }
 
-void tst_QMutex::try_lock_for_non_recursive() {
-#if !__has_include(<chrono>)
-    QSKIP("This test requires <chrono>");
-#else
+void tst_QMutex::try_lock_for_non_recursive()
+{
     class Thread : public QThread
     {
     public:
@@ -451,14 +439,10 @@ void tst_QMutex::try_lock_for_non_recursive() {
     testsTurn.acquire();
     threadsTurn.release();
     thread.wait();
-#endif
 }
 
 void tst_QMutex::try_lock_until_non_recursive()
 {
-#if !__has_include(<chrono>)
-    QSKIP("This test requires <chrono>");
-#else
     class Thread : public QThread
     {
     public:
@@ -580,7 +564,6 @@ void tst_QMutex::try_lock_until_non_recursive()
     testsTurn.acquire();
     threadsTurn.release();
     thread.wait();
-#endif
 }
 
 void tst_QMutex::tryLock_recursive()
@@ -709,9 +692,6 @@ void tst_QMutex::tryLock_recursive()
 
 void tst_QMutex::try_lock_for_recursive()
 {
-#if !__has_include(<chrono>)
-    QSKIP("This test requires <chrono>");
-#else
     class Thread : public QThread
     {
     public:
@@ -832,14 +812,10 @@ void tst_QMutex::try_lock_for_recursive()
     testsTurn.acquire();
     threadsTurn.release();
     thread.wait();
-#endif
 }
 
 void tst_QMutex::try_lock_until_recursive()
 {
-#if !__has_include(<chrono>)
-    QSKIP("This test requires <chrono>");
-#else
     class Thread : public QThread
     {
     public:
@@ -961,7 +937,6 @@ void tst_QMutex::try_lock_until_recursive()
     testsTurn.acquire();
     threadsTurn.release();
     thread.wait();
-#endif
 }
 
 class mutex_Thread : public QThread