diff --git a/climada/engine/impact.py b/climada/engine/impact.py
index 26043290d..c7d956883 100644
--- a/climada/engine/impact.py
+++ b/climada/engine/impact.py
@@ -46,7 +46,6 @@
 from scipy import sparse
 from tqdm import tqdm
 
-import climada.util.checker as u_check
 import climada.util.coordinates as u_coord
 import climada.util.dates_times as u_dt
 import climada.util.interpolation as u_interp
@@ -549,7 +548,7 @@ def local_exceedance_impact(
             )
 
         # check frequency unit
-        return_period_unit = u_check.convert_frequency_unit_to_time_unit(
+        return_period_unit = u_dt.convert_frequency_unit_to_time_unit(
             self.frequency_unit
         )
 
diff --git a/climada/hazard/base.py b/climada/hazard/base.py
index bdb76c354..b97396083 100644
--- a/climada/hazard/base.py
+++ b/climada/hazard/base.py
@@ -538,7 +538,7 @@ def local_exceedance_intensity(
         if not min_intensity and min_intensity != 0:
             min_intensity = self.intensity_thres
         # check frequency unit
-        return_period_unit = u_check.convert_frequency_unit_to_time_unit(
+        return_period_unit = u_dt.convert_frequency_unit_to_time_unit(
             self.frequency_unit
         )
 
@@ -659,7 +659,7 @@ def local_return_period(
         if not min_intensity and min_intensity != 0:
             min_intensity = self.intensity_thres
         # check frequency unit
-        return_period_unit = u_check.convert_frequency_unit_to_time_unit(
+        return_period_unit = u_dt.convert_frequency_unit_to_time_unit(
             self.frequency_unit
         )
 
diff --git a/climada/util/checker.py b/climada/util/checker.py
index 8fa977ed7..0d17b6036 100644
--- a/climada/util/checker.py
+++ b/climada/util/checker.py
@@ -228,32 +228,3 @@ def prune_csr_matrix(matrix: sparse.csr_matrix):
     matrix.check_format()
     matrix.eliminate_zeros()
     matrix.sum_duplicates()
-
-
-def convert_frequency_unit_to_time_unit(frequency_unit):
-    """Converts common frequency units to corresponding time units. Unknown frequency
-    units are converted to "years".
-
-    Parameters
-    ----------
-    frequency_unit : str
-        unit of frequency
-
-    Returns
-    -------
-    str
-        corresponding time unit.
-    """
-    if frequency_unit in ["1/year", "annual", "1/y", "1/a"]:
-        time_unit = "years"
-    elif frequency_unit in ["1/month", "monthly", "1/m"]:
-        time_unit = "months"
-    elif frequency_unit in ["1/week", "weekly", "1/w"]:
-        time_unit = "weeks"
-    else:
-        LOGGER.warning(
-            f"Frequency unit {frequency_unit} is not known, "
-            "years will be used as time unit."
-        )
-        time_unit = "years"
-    return time_unit
diff --git a/climada/util/dates_times.py b/climada/util/dates_times.py
index 07882bf11..87453b0ae 100644
--- a/climada/util/dates_times.py
+++ b/climada/util/dates_times.py
@@ -114,3 +114,32 @@ def first_year(ordinal_vector):
     int
     """
     return dt.date.fromordinal(np.min(ordinal_vector)).year
+
+
+def convert_frequency_unit_to_time_unit(frequency_unit):
+    """Converts common frequency units to corresponding time units. Unknown frequency
+    units are converted to "years".
+
+    Parameters
+    ----------
+    frequency_unit : str
+        unit of frequency
+
+    Returns
+    -------
+    str
+        corresponding time unit.
+    """
+    if frequency_unit in ["1/year", "annual", "1/y", "1/a"]:
+        time_unit = "years"
+    elif frequency_unit in ["1/month", "monthly", "1/m"]:
+        time_unit = "months"
+    elif frequency_unit in ["1/week", "weekly", "1/w"]:
+        time_unit = "weeks"
+    else:
+        LOGGER.warning(
+            f"Frequency unit {frequency_unit} is not known, "
+            "years will be used as time unit."
+        )
+        time_unit = "years"
+    return time_unit
diff --git a/climada/util/test/test_checker.py b/climada/util/test/test_checker.py
index ab6a0882c..493f394e4 100644
--- a/climada/util/test/test_checker.py
+++ b/climada/util/test/test_checker.py
@@ -140,18 +140,6 @@ def test_prune_csr_matrix(self):
         np.testing.assert_array_equal(matrix.data, [3])
         self.assertEqual(matrix.nnz, 1)
 
-    def test_convert_frequency_unit_to_time_unit(self):
-        # test frequency unit to time unit conversion
-        frequency_units = ["1/year", "1/y", "1/month", "1/week", "", "unknown"]
-        time_units = ["years", "years", "months", "weeks", "years", "years"]
-        np.testing.assert_equal(
-            time_units,
-            [
-                u_check.convert_frequency_unit_to_time_unit(frequency_unit)
-                for frequency_unit in frequency_units
-            ],
-        )
-
 
 # Execute Tests
 if __name__ == "__main__":
diff --git a/climada/util/test/test_dates_times.py b/climada/util/test/test_dates_times.py
index 3cc9d25bc..b4b1dfc84 100644
--- a/climada/util/test/test_dates_times.py
+++ b/climada/util/test/test_dates_times.py
@@ -88,8 +88,25 @@ def test_first_year_pass(self):
         self.assertEqual(u_dt.first_year(np.array(ordinal_date)), 1918)
 
 
+class TestUnitConversion(unittest.TestCase):
+    """Test time and frequency conversion functions"""
+
+    def test_convert_frequency_unit_to_time_unit(self):
+        # test frequency unit to time unit conversion
+        frequency_units = ["1/year", "1/y", "1/month", "1/week", "", "unknown"]
+        time_units = ["years", "years", "months", "weeks", "years", "years"]
+        np.testing.assert_equal(
+            time_units,
+            [
+                u_dt.convert_frequency_unit_to_time_unit(frequency_unit)
+                for frequency_unit in frequency_units
+            ],
+        )
+
+
 # Execute Tests
 if __name__ == "__main__":
     TESTS = unittest.TestLoader().loadTestsFromTestCase(TestDateString)
     TESTS.addTests(unittest.TestLoader().loadTestsFromTestCase(TestDateNumpy))
+    TESTS.addTests(unittest.TestLoader().loadTestsFromTestCase(TestUnitConversion))
     unittest.TextTestRunner(verbosity=2).run(TESTS)