diff --git a/src/corelib/time/qdatetime.cpp b/src/corelib/time/qdatetime.cpp
index 1f401948cc..7d11605671 100644
--- a/src/corelib/time/qdatetime.cpp
+++ b/src/corelib/time/qdatetime.cpp
@@ -1297,6 +1297,25 @@ QString QDate::toString(QStringView format, QCalendar cal) const
 {
     return QLocale::c().toString(*this, format, cal);
 }
+
+// Out-of-line no-calendar overloads, since QCalendar is a non-trivial type
+/*!
+    \overload
+    \since 5.10
+*/
+QString QDate::toString(QStringView format) const
+{
+    return QLocale::c().toString(*this, format, QCalendar());
+}
+
+/*!
+    \overload
+    \since 4.6
+*/
+QString QDate::toString(const QString &format) const
+{
+    return QLocale::c().toString(*this, qToStringViewIgnoringNull(format), QCalendar());
+}
 #endif // datestring
 
 /*!
@@ -4689,6 +4708,25 @@ QString QDateTime::toString(QStringView format, QCalendar cal) const
 {
     return QLocale::c().toString(*this, format, cal);
 }
+
+// Out-of-line no-calendar overloads, since QCalendar is a non-trivial type
+/*!
+    \overload
+    \since 5.10
+*/
+QString QDateTime::toString(QStringView format) const
+{
+    return QLocale::c().toString(*this, format, QCalendar());
+}
+
+/*!
+    \overload
+    \since 4.6
+*/
+QString QDateTime::toString(const QString &format) const
+{
+    return QLocale::c().toString(*this, qToStringViewIgnoringNull(format), QCalendar());
+}
 #endif // datestring
 
 static inline void massageAdjustedDateTime(QDateTimeData &d, QDate date, QTime time, bool forward)
diff --git a/src/corelib/time/qdatetime.h b/src/corelib/time/qdatetime.h
index cec7771a8d..1474e2c6f4 100644
--- a/src/corelib/time/qdatetime.h
+++ b/src/corelib/time/qdatetime.h
@@ -102,9 +102,11 @@ public:
 
 #if QT_CONFIG(datestring)
     QString toString(Qt::DateFormat format = Qt::TextDate) const;
-    QString toString(const QString &format, QCalendar cal = QCalendar()) const
+    QString toString(const QString &format) const;
+    QString toString(const QString &format, QCalendar cal) const
     { return toString(qToStringViewIgnoringNull(format), cal); }
-    QString toString(QStringView format, QCalendar cal = QCalendar()) const;
+    QString toString(QStringView format) const;
+    QString toString(QStringView format, QCalendar cal) const;
 #endif
     bool setDate(int year, int month, int day); // Gregorian-optimized
     bool setDate(int year, int month, int day, QCalendar cal);
@@ -409,9 +411,11 @@ public:
 
 #if QT_CONFIG(datestring)
     QString toString(Qt::DateFormat format = Qt::TextDate) const;
-    QString toString(const QString &format, QCalendar cal = QCalendar()) const
+    QString toString(const QString &format) const;
+    QString toString(const QString &format, QCalendar cal) const
     { return toString(qToStringViewIgnoringNull(format), cal); }
-    QString toString(QStringView format, QCalendar cal = QCalendar()) const;
+    QString toString(QStringView format) const;
+    QString toString(QStringView format, QCalendar cal) const;
 #endif
     [[nodiscard]] QDateTime addDays(qint64 days) const;
     [[nodiscard]] QDateTime addMonths(int months) const;