diff --git a/esmvalcore/cmor/_fixes/icon/icon.py b/esmvalcore/cmor/_fixes/icon/icon.py
index 8a170eb730..5200cfed33 100644
--- a/esmvalcore/cmor/_fixes/icon/icon.py
+++ b/esmvalcore/cmor/_fixes/icon/icon.py
@@ -270,25 +270,29 @@ def _fix_time(self, cube, cubes):
         new_t_unit = cf_units.Unit('days since 1850-01-01',
                                    calendar='proleptic_gregorian')
 
-        # New routine to convert time of daily and hourly data
-        # The string %f (fraction of day) is not a valid format string
-        # for datetime.strptime, so we have to convert it ourselves
-        time_str = [str(x) for x in time_coord.points]
-
-        # First, extract date (year, month, day) from string
-        # and convert it to datetime object
-        year_month_day_str = pd.Series(time_str).str.extract(
-            r'(\d*)\.?\d*', expand=False
-        )
+        # New routine to convert time of daily and hourly data. The string %f
+        # (fraction of day) is not a valid format string for datetime.strptime,
+        # so we have to convert it ourselves.
+        time_str = pd.Series(time_coord.points, dtype=str)
+
+        # First, extract date (year, month, day) from string and convert it to
+        # datetime object
+        year_month_day_str = time_str.str.extract(r'(\d*)\.?\d*', expand=False)
         year_month_day = pd.to_datetime(year_month_day_str, format='%Y%m%d')
+
         # Second, extract day fraction and convert it to timedelta object
-        day_float_str = pd.Series(time_str).str.extract(
+        day_float_str = time_str.str.extract(
             r'\d*(\.\d*)', expand=False
         ).fillna('0.0')
         day_float = pd.to_timedelta(day_float_str.astype(float), unit='D')
-        # Finally, add date and day fraction to get final datetime
-        # and convert it to correct units
-        new_datetimes = (year_month_day + day_float).dt.to_pydatetime()
+
+        # Finally, add date and day fraction to get final datetime and convert
+        # it to correct units. Note: we also round to next second, otherwise
+        # this results in times that are off by 1s (e.g., 13:59:59 instead of
+        # 14:00:00).
+        new_datetimes = (year_month_day + day_float).round(
+            'S'
+        ).dt.to_pydatetime()
         new_dt_points = date2num(np.array(new_datetimes), new_t_unit)
 
         time_coord.points = new_dt_points
diff --git a/tests/integration/cmor/_fixes/icon/test_icon.py b/tests/integration/cmor/_fixes/icon/test_icon.py
index e7f714beef..87ac889ff2 100644
--- a/tests/integration/cmor/_fixes/icon/test_icon.py
+++ b/tests/integration/cmor/_fixes/icon/test_icon.py
@@ -1346,13 +1346,13 @@ def test_hourly_data(cubes_2d):
     """Test fix."""
     fix = get_allvars_fix('Amon', 'tas')
     for cube in cubes_2d:
-        cube.coord('time').points = [20220314.1]
+        cube.coord('time').points = [20041104.5833333]
 
     fixed_cubes = fix.fix_metadata(cubes_2d)
 
     cube = check_tas_metadata(fixed_cubes)
     date = cube.coord('time').units.num2date(cube.coord('time').points)
-    np.testing.assert_array_equal(date, [datetime(2022, 3, 14, 2, 24)])
+    np.testing.assert_array_equal(date, [datetime(2004, 11, 4, 14, 0)])
     assert cube.coord('time').bounds is None