diff --git a/src/backend/core/column/ColumnPrivate.cpp b/src/backend/core/column/ColumnPrivate.cpp
index 60e16a445f1537e1e4ed581d471450c84ef90f66..af7ae500ff1ea93468d7585071a89c9bab5f9495 100644
--- a/src/backend/core/column/ColumnPrivate.cpp
+++ b/src/backend/core/column/ColumnPrivate.cpp
@@ -353,21 +353,21 @@ void ColumnPrivate::setColumnMode(AbstractColumn::ColumnMode mode) {
 			break;
 		case AbstractColumn::ColumnMode::Numeric:
 			filter = new String2DoubleFilter();
-			//TODO: set number locale
+			static_cast<String2DoubleFilter*>(filter)->setNumberLocale(numberLocale);
 			filter_is_temporary = true;
 			temp_col = new Column("temp_col", *(static_cast<QVector<QString>*>(old_data)), m_column_mode);
 			m_data = new QVector<double>();
 			break;
 		case AbstractColumn::ColumnMode::Integer:
 			filter = new String2IntegerFilter();
-			//TODO: set number locale
+			static_cast<String2IntegerFilter*>(filter)->setNumberLocale(numberLocale);
 			filter_is_temporary = true;
 			temp_col = new Column("temp_col", *(static_cast<QVector<QString>*>(old_data)), m_column_mode);
 			m_data = new QVector<int>();
 			break;
 		case AbstractColumn::ColumnMode::BigInt:
 			filter = new String2BigIntFilter();
-			//TODO: set number locale
+			static_cast<String2BigIntFilter*>(filter)->setNumberLocale(numberLocale);
 			filter_is_temporary = true;
 			temp_col = new Column("temp_col", *(static_cast<QVector<QString>*>(old_data)), m_column_mode);
 			m_data = new QVector<qint64>();
diff --git a/src/backend/datasources/filters/AbstractFileFilter.cpp b/src/backend/datasources/filters/AbstractFileFilter.cpp
index b8b4679471604e0bf318b707769e7665c8553089..6a27a7c8cfdb9f5067a01772947a9919888bac44 100644
--- a/src/backend/datasources/filters/AbstractFileFilter.cpp
+++ b/src/backend/datasources/filters/AbstractFileFilter.cpp
@@ -44,17 +44,13 @@ bool AbstractFileFilter::isNan(const QString& s) {
 
 	return false;
 }
-AbstractColumn::ColumnMode AbstractFileFilter::columnMode(const QString& valueString, const QString& dateTimeFormat) {
-	QLocale locale;
-	return columnMode(valueString, dateTimeFormat, locale);
-}
 
 AbstractColumn::ColumnMode AbstractFileFilter::columnMode(const QString& valueString, const QString& dateTimeFormat, QLocale::Language lang) {
-	QLocale locale(lang);
-	return columnMode(valueString, dateTimeFormat, locale);
+	return columnMode(valueString, dateTimeFormat, QLocale(lang));
 }
 
 AbstractColumn::ColumnMode AbstractFileFilter::columnMode(const QString& valueString, const QString& dateTimeFormat, const QLocale& locale) {
+	DEBUG("AbstractFileFilter::columnMode()")
 
 	//TODO: use BigInt as default integer?
 	if (valueString.size() == 0)	// empty string treated as integer (meaning the non-empty strings will determine the data type)
diff --git a/src/backend/datasources/filters/AbstractFileFilter.h b/src/backend/datasources/filters/AbstractFileFilter.h
index 5c14880376de4886dab5228fb7846a9553576e9f..982eadc80054ebc15d229280244ab2b9764f96c1 100644
--- a/src/backend/datasources/filters/AbstractFileFilter.h
+++ b/src/backend/datasources/filters/AbstractFileFilter.h
@@ -51,9 +51,8 @@ public:
 	~AbstractFileFilter() override = default;
 
 	static bool isNan(const QString&);
-	static AbstractColumn::ColumnMode columnMode(const QString& valueString, const QString& dateTimeFormat);
 	static AbstractColumn::ColumnMode columnMode(const QString& valueString, const QString& dateTimeFormat, QLocale::Language);
-	static AbstractColumn::ColumnMode columnMode(const QString& valueString, const QString& dateTimeFormat, const QLocale&);
+	static AbstractColumn::ColumnMode columnMode(const QString& valueString, const QString& dateTimeFormat, const QLocale& = QLocale());
 	static QStringList numberFormats();
 	static AbstractFileFilter::FileType fileType(const QString&);
 	static QStringList fileTypes();
diff --git a/src/commonfrontend/spreadsheet/SpreadsheetView.cpp b/src/commonfrontend/spreadsheet/SpreadsheetView.cpp
index 489308547cb23658be29dcb8d865a3ce464d92b3..90334c4408efbc479936f5d6493be736d7189dc9 100644
--- a/src/commonfrontend/spreadsheet/SpreadsheetView.cpp
+++ b/src/commonfrontend/spreadsheet/SpreadsheetView.cpp
@@ -1540,7 +1540,7 @@ void SpreadsheetView::pasteIntoSelection() {
 // 			if (!localeDetermined)
 // 				localeDetermined = determineLocale(nonEmptyValue, locale);
 
-			const auto mode = AbstractFileFilter::columnMode(nonEmptyValue, QLatin1String("yyyy-dd-MM hh:mm:ss:zzz"));
+			const auto mode = AbstractFileFilter::columnMode(nonEmptyValue, QLatin1String("yyyy-dd-MM hh:mm:ss:zzz"), numberLocale);
 			col->setColumnMode(mode);
 		}
 
@@ -1560,7 +1560,7 @@ void SpreadsheetView::pasteIntoSelection() {
 // 				if (!localeDetermined)
 // 					localeDetermined = determineLocale(nonEmptyValue, locale);
 
-				const auto mode = AbstractFileFilter::columnMode(nonEmptyValue, QLatin1String("yyyy-dd-MM hh:mm:ss:zzz"));
+				const auto mode = AbstractFileFilter::columnMode(nonEmptyValue, QLatin1String("yyyy-dd-MM hh:mm:ss:zzz"), numberLocale);
 				Column* new_col = new Column(QString::number(curCol), mode);
 				new_col->setPlotDesignation(AbstractColumn::PlotDesignation::Y);
 				new_col->insertRows(0, m_spreadsheet->rowCount());