[utils] Add another date format pattern (#14999)

test/test_utils.py

@@ -343,6 +343,7 @@ class TestUtil(unittest.TestCase):
         self.assertEqual(unified_timestamp('Feb 7, 2016 at 6:35 pm'), 1454870100)
         self.assertEqual(unified_timestamp('2017-03-30T17:52:41Q'), 1490896361)
         self.assertEqual(unified_timestamp('Sep 11, 2013 | 5:49 AM'), 1378878540)
+        self.assertEqual(unified_timestamp('December 15, 2017 at 7:49 am'), 1513324140)
 
     def test_determine_ext(self):
         self.assertEqual(determine_ext('http://example.com/foo/bar.mp4/?download'), 'mp4')

youtube_dl/utils.py

@@ -159,6 +159,8 @@ DATE_FORMATS = (
     '%Y-%m-%dT%H:%M',
     '%b %d %Y at %H:%M',
     '%b %d %Y at %H:%M:%S',
+    '%B %d %Y at %H:%M',
+    '%B %d %Y at %H:%M:%S',
 )
 
 DATE_FORMATS_DAY_FIRST = list(DATE_FORMATS)