Add tests for %I and %p format options

test/date_test/parse.pass.cpp

@@ -623,6 +623,21 @@ test_p()
         assert(!in.bad());
         assert(tp == sys_days{2016_y/12/11} + hours{23});
     }
+    {
+        std::istringstream in{"1986-12-01 01:01:01 pm"};
+        sys_time<seconds> tp;
+        in >> parse("%Y-%m-%d %I:%M:%S %p", tp);
+        assert(!in.fail());
+        assert(!in.bad());
+        assert(tp == sys_days{1986_y/12/01} + hours{13} + minutes{01} + seconds{01});
+    }
+    {
+        std::istringstream in{"1986-12-01 01:01:01"};
+        sys_time<seconds> tp;
+        in >> parse("%Y-%m-%d %I:%M:%S", tp);
+        // The test will fail because %I needs the %p option to shows if it is AM or PM
+        assert(in.fail());
+    }
 }
 
 void