diff --git a/releasenotes/notes/deprecate-str-dates-on-get_test_counts_in_date_range-b16d285cab135d52.yaml b/releasenotes/notes/deprecate-str-dates-on-get_test_counts_in_date_range-b16d285cab135d52.yaml
new file mode 100644
index 0000000..146c33d
--- /dev/null
+++ b/releasenotes/notes/deprecate-str-dates-on-get_test_counts_in_date_range-b16d285cab135d52.yaml
@@ -0,0 +1,10 @@
+---
+deprecations:
+    - Passing in the date as a string in the format "%b %d %Y" to the function
+      get_test_counts_in_date_rage() in the DB API. Instead pass the date in
+      as a datetime object.
+fixes:
+  - Setting the date as an ISO8601, as indicated by the docs and --help, for
+    the subunit2sql-graph command agg_count will now work correctly. It would
+    previously stack trace. (Story 2000581)
+
diff --git a/subunit2sql/analysis/agg_count.py b/subunit2sql/analysis/agg_count.py
index 7e3806c..49da590 100644
--- a/subunit2sql/analysis/agg_count.py
+++ b/subunit2sql/analysis/agg_count.py
@@ -12,6 +12,7 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+from dateutil import parser as date_parser
 from oslo_config import cfg
 import pandas as pd
 
@@ -48,13 +49,19 @@ def generate_series():
                     'failure': int(test.failure),
                 }
     else:
+        start_date = None
+        stop_date = None
+        if CONF.start_date:
+            start_date = date_parser.parse(CONF.start_date)
+        if CONF.stop_date:
+            stop_date = date_parser.parse(CONF.stop_date)
         if CONF.command.test_ids:
             ids = [api.get_id_from_test_id(x) for x in CONF.command.test_ids]
         else:
             ids = api.get_ids_for_all_tests(session)
         for test in ids:
             test_dict[test] = api.get_test_counts_in_date_range(
-                test, CONF.start_date, CONF.stop_date, session)
+                test, start_date, stop_date, session)
     if CONF.command.no_success_graph:
         for test in test_dict:
             test_dict[test].pop('success')
diff --git a/subunit2sql/db/api.py b/subunit2sql/db/api.py
index 4532c90..2356616 100644
--- a/subunit2sql/db/api.py
+++ b/subunit2sql/db/api.py
@@ -1209,14 +1209,22 @@ def get_test_counts_in_date_range(test_id, start_date=None, stop_date=None,
     certain date range
 
     :param str test_id: The test_id's ID(big integer) to identify the test
-    :param str start_date: The date to use as the start for counting
-    :param str stop_date: The date to use as the cutoff for counting
+    :param datetime start_date: The date to use as the start for counting. A
+                                str in the datetime str format "%b %d %Y" was
+                                the previous format here and will still work
+                                but is deprecated in favor of passing in a
+                                datetime object.
+    :param datetime stop_date: The date to use as the cutoff for counting. A
+                               str in the datetime str format "%b %d %Y" was
+                               the previous format here and will still work but
+                               is deprecated in favor of passing in a datetime.
     :param session: Optional session object if one isn't provided a new session
                     will be acquired for the duration of this operation
     :return: A dict containing the number of successes, failures, and skips
     :rtype: dict
     """
-    start_date = datetime.datetime.strptime(start_date, '%b %d %Y')
+    if isinstance(start_date, str):
+        start_date = datetime.datetime.strptime(start_date, '%b %d %Y')
     if isinstance(stop_date, str):
         stop_date = datetime.datetime.strptime(stop_date, '%b %d %Y')
     session = session or get_session()
diff --git a/subunit2sql/tests/db/test_api.py b/subunit2sql/tests/db/test_api.py
index 7c76aee..8dfb17b 100644
--- a/subunit2sql/tests/db/test_api.py
+++ b/subunit2sql/tests/db/test_api.py
@@ -949,7 +949,7 @@ class TestDatabaseAPI(base.TestCase):
         self.assertIn(run_b.uuid, res)
         self.assertIn(run_c.uuid, res)
 
-    def test_get_test_counts_in_date_range(self):
+    def test_get_test_counts_in_date_range_as_str(self):
         timestamp_str_a = 'Dec 01 2015'
         timestamp_str_b = 'Dec 20 2015'
         timestamp_a = datetime.datetime(2015, 12, 2, 10, 00, 00)
@@ -976,6 +976,33 @@ class TestDatabaseAPI(base.TestCase):
         self.assertEqual(1, res['failure'])
         self.assertEqual(0, res['skips'])
 
+    def test_get_test_counts_in_date_range(self):
+        timestamp_a = datetime.datetime(2015, 12, 2, 10, 00, 00)
+        timestamp_b = timestamp_a + datetime.timedelta(minutes=10)
+        timestamp_c = timestamp_a + datetime.timedelta(minutes=20)
+        timestamp_d = datetime.datetime(2015, 12, 22, 10, 00, 00)
+        timerange_a = datetime.datetime(2015, 12, 1)
+        timerange_b = datetime.datetime(2015, 12, 20)
+        run_a = api.create_run()
+        run_b = api.create_run()
+        run_c = api.create_run()
+        run_d = api.create_run()
+        test = api.create_test('fake_test')
+        api.create_test_run(test.id, run_a.id, 'success',
+                            timestamp_a, timestamp_b)
+        api.create_test_run(test.id, run_b.id, 'fail',
+                            timestamp_a, timestamp_c)
+        api.create_test_run(test.id, run_c.id, 'success',
+                            timestamp_a, timestamp_d)
+        api.create_test_run(test.id, run_d.id, 'skip',
+                            timestamp_c, timestamp_d)
+        res = api.get_test_counts_in_date_range(test.id,
+                                                timerange_a,
+                                                timerange_b)
+        self.assertEqual(1, res['success'])
+        self.assertEqual(1, res['failure'])
+        self.assertEqual(0, res['skips'])
+
     def test_get_failing_test_ids_from_runs_by_key_value(self):
         test_a = api.create_test('fake_test')
         test_b = api.create_test('fake_test1')