datetime format is encoded (instead of pure ASCII characters transformed into string)

Here is a reference regarding discovering encoding for strftime in Python. https://stackoverflow.com/questions/19412915/how-determine-encoding-of-datetime-strftime-in-python

Closes #194 (closed)

smash/web/tests/test_statistics.py

@@ -40,7 +40,7 @@ class TestStatistics(TestCase):
         statistics = self.statistics_manager.get_statistics_for_month(self.now.month, self.now.year)
         self.check_statistics(statistics, 0, 0, 1, {"C": [1, 1]}, ['Scheduled'])
 
-        statistics = self.statistics_manager.get_statistics_for_month(self.visit_end.month, self.now.year)
+        statistics = self.statistics_manager.get_statistics_for_month(self.visit_end.month, self.visit_end.year)
         self.check_statistics(statistics, 0, 1, 0, {"C": [0, 0]}, ['Scheduled'])
 
     def test_get_statistics_for_month_one_appointment_visit(self):