diff --git a/app/__init__.py b/app/__init__.py
index 51cb3a268..d84939125 100644
--- a/app/__init__.py
+++ b/app/__init__.py
@@ -386,9 +386,9 @@ def format_delta(date):
 def format_delta_days(date):
     now = datetime.now(timezone.utc)
     date = utc_string_to_aware_gmt_datetime(date)
-    if date.strftime('%Y-%M-%D') == now.strftime('%Y-%M-%D'):
+    if date.strftime('%Y-%m-%d') == now.strftime('%Y-%m-%d'):
         return "today"
-    if date.strftime('%Y-%M-%D') == (now - timedelta(days=1)).strftime('%Y-%M-%D'):
+    if date.strftime('%Y-%m-%d') == (now - timedelta(days=1)).strftime('%Y-%m-%d'):
         return "yesterday"
     return naturaltime_without_indefinite_article(now - date)
 
diff --git a/tests/app/main/views/test_dashboard.py b/tests/app/main/views/test_dashboard.py
index 34d29dbd7..b83c16b28 100644
--- a/tests/app/main/views/test_dashboard.py
+++ b/tests/app/main/views/test_dashboard.py
@@ -497,7 +497,21 @@ def test_returned_letters_not_visible_if_service_has_no_returned_letters(
     assert not page.select('#total-returned-letters')
 
 
-@freeze_time('2020-01-10')
+@pytest.mark.parametrize('reporting_date, expected_message', (
+    ('2020-01-10 00:00:00.000000', (
+        '4,000 returned letters latest report today'
+    )),
+    ('2020-01-09 23:59:59.000000', (
+        '4,000 returned letters latest report yesterday'
+    )),
+    ('2020-01-08 12:12:12.000000', (
+        '4,000 returned letters latest report 2 days ago'
+    )),
+    ('2019-12-10 00:00:00.000000', (
+        '4,000 returned letters latest report 1 month ago'
+    )),
+))
+@freeze_time('2020-01-10 12:34:00.000000')
 def test_returned_letters_shows_count_of_recently_returned_letters(
     client_request,
     mocker,
@@ -509,12 +523,14 @@ def test_returned_letters_shows_count_of_recently_returned_letters(
     mock_get_usage,
     mock_get_free_sms_fragment_limit,
     mock_get_inbound_sms_summary,
+    reporting_date,
+    expected_message,
 ):
     mocker.patch(
         'app.service_api_client.get_returned_letter_statistics',
         return_value={
             'returned_letter_count': 4000,
-            'most_recent_report': '2020-01-10',
+            'most_recent_report': reporting_date,
         },
     )
     page = client_request.get(
@@ -522,9 +538,7 @@ def test_returned_letters_shows_count_of_recently_returned_letters(
         service_id=SERVICE_ONE_ID,
     )
     banner = page.select_one('#total-returned-letters')
-    assert normalize_spaces(
-        banner.text
-    ) == '4,000 returned letters latest report today'
+    assert normalize_spaces(banner.text) == expected_message
     assert banner['href'] == url_for(
         'main.returned_letter_summary', service_id=SERVICE_ONE_ID
     )