diff --git a/gramps/gen/filters/rules/test/event_rules_test.py b/gramps/gen/filters/rules/test/event_rules_test.py
index 010706996..98dd227df 100644
--- a/gramps/gen/filters/rules/test/event_rules_test.py
+++ b/gramps/gen/filters/rules/test/event_rules_test.py
@@ -28,6 +28,7 @@ from ....db.utils import import_as_dict
 from ....filters import GenericFilterFactory
 from ....const import DATA_DIR
 from ....user import User
+from ....utils.unittest import localize_date
 
 from ..event import (
     AllEvents, HasType, HasIdOf, HasGallery, RegExpIdOf, HasCitation, HasNote,
@@ -171,7 +172,8 @@ class BaseTest(unittest.TestCase):
         """
         Test HasData rule.
         """
-        rule = HasData(['Burial', 'before 1800', 'USA', ''])
+        date_str = localize_date('before 1800')
+        rule = HasData(['Burial', date_str, 'USA', ''])
         self.assertEqual(self.filter_with_rule(rule), set([
             'a5af0ed4211095487d2', 'a5af0ed36793c1d3e05',
             'a5af0ecfcc16ce7a96a']))
diff --git a/gramps/gen/filters/rules/test/family_rules_test.py b/gramps/gen/filters/rules/test/family_rules_test.py
index 7b626e788..7ff0b6e8d 100644
--- a/gramps/gen/filters/rules/test/family_rules_test.py
+++ b/gramps/gen/filters/rules/test/family_rules_test.py
@@ -28,6 +28,7 @@ from ....db.utils import import_as_dict
 from ....filters import GenericFilterFactory
 from ....const import DATA_DIR
 from ....user import User
+from ....utils.unittest import localize_date
 
 from ..family import (
     AllFamilies, HasRelType, HasGallery, HasIdOf, HasLDS, HasNote, RegExpIdOf,
@@ -176,7 +177,8 @@ class BaseTest(unittest.TestCase):
         """
         Test HasEvent rule.
         """
-        rule = HasEvent(['Marriage', 'before 1900', 'USA', '', 'Garner'])
+        date_str = localize_date('before 1900')
+        rule = HasEvent(['Marriage', date_str, 'USA', '', 'Garner'])
         self.assertEqual(self.filter_with_rule(rule), set([
             'KSFKQCP4V0YXGM1LR9', '8ZFKQC3FRSHACOJBOU', '3XFKQCE7QUDJ99AVNV',
             'OVFKQC51DX0OQUV3JB', '9OUJQCBOHW9UEK9CNV']))
diff --git a/gramps/gen/filters/rules/test/person_rules_test.py b/gramps/gen/filters/rules/test/person_rules_test.py
index beb982f22..84f772579 100644
--- a/gramps/gen/filters/rules/test/person_rules_test.py
+++ b/gramps/gen/filters/rules/test/person_rules_test.py
@@ -32,6 +32,7 @@ from ....db.utils import import_as_dict
 from ....filters import GenericFilter, CustomFilters
 from ....const import DATA_DIR
 from ....user import User
+from ....utils.unittest import localize_date
 
 from ..person import (
     Disconnected, Everyone, FamilyWithIncompleteEvent, HasAddress,
@@ -238,7 +239,8 @@ class BaseTest(unittest.TestCase):
         """
         Test rule.
         """
-        rule = HasBirth(['between 1600 and 1700', 'akron', ''])
+        date_str = localize_date('between 1600 and 1700')
+        rule = HasBirth([date_str, 'akron', ''])
         res = self.filter_with_rule(rule)
         self.assertEqual(len(res), 2)
 
@@ -246,7 +248,8 @@ class BaseTest(unittest.TestCase):
         """
         Test HasDeath rule.
         """
-        rule = HasDeath(['between 1600 and 1700', 'ashtabula', ''])
+        date_str = localize_date('between 1600 and 1700')
+        rule = HasDeath([date_str, 'ashtabula', ''])
         res = self.filter_with_rule(rule)
         self.assertEqual(len(res), 2)
 
@@ -254,8 +257,8 @@ class BaseTest(unittest.TestCase):
         """
         Test rule.
         """
-        rule = HasEvent(['Birth', 'between 1600 and 1700', 'akron',
-                         '', '', 1])
+        date_str = localize_date('between 1600 and 1700')
+        rule = HasEvent(['Birth', date_str, 'akron', '', '', 1])
         res = self.filter_with_rule(rule)
         self.assertEqual(len(res), 2)
 
@@ -271,7 +274,8 @@ class BaseTest(unittest.TestCase):
         """
         Test rule.
         """
-        rule = HasFamilyEvent(['Marriage', 'after 1900', 'craw', ''])
+        date_str = localize_date('after 1900')
+        rule = HasFamilyEvent(['Marriage', date_str, 'craw', ''])
         res = self.filter_with_rule(rule)
         self.assertEqual(len(res), 4)
 
diff --git a/gramps/gen/utils/unittest.py b/gramps/gen/utils/unittest.py
new file mode 100644
index 000000000..f2c89dc26
--- /dev/null
+++ b/gramps/gen/utils/unittest.py
@@ -0,0 +1,46 @@
+#
+# Gramps - a GTK+/GNOME based genealogy program
+#
+# Copyright (C) 2022 Nick Hall
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+#
+
+"""
+Utilities used in unit tests.
+"""
+
+#-------------------------------------------------------------------------
+#
+# Gramps classes
+#
+#-------------------------------------------------------------------------
+from ..utils.grampslocale import GrampsLocale
+
+#-------------------------------------------------------------------------
+#
+# Unit test utilities
+#
+#-------------------------------------------------------------------------
+
+parser = GrampsLocale(lang='en').date_parser
+displayer = GrampsLocale().date_displayer
+
+def localize_date(date_str):
+    """
+    Translate a date into the current locale.
+    """
+    date = parser.parse(date_str)
+    return displayer.display(date)
diff --git a/po/POTFILES.skip b/po/POTFILES.skip
index 5237f422e..17747b8bb 100644
--- a/po/POTFILES.skip
+++ b/po/POTFILES.skip
@@ -280,6 +280,7 @@ gramps/gen/utils/lru.py
 gramps/gen/utils/maclocale.py
 gramps/gen/utils/resourcepath.py
 gramps/gen/utils/thumbnails.py
+gramps/gen/utils/unittest.py
 #
 # gen.utils.docgen
 #