class Day:
     """Individual days defined by their dates."""
 
-    def __init__(self, date: str):
+    def __init__(self, date: str, comment: str = ''):
         self.date = date
         self.datetime = date_valid(self.date)
         if not self.datetime:
             raise HandledException(f'Given date of wrong format: {self.date}')
+        self.comment = comment
 
     def __eq__(self, other: object):
         return isinstance(other, self.__class__) and self.date == other.date
     @classmethod
     def from_table_row(cls, row: Row):
         """Make new Day from database row."""
-        return cls(row[0])
+        return cls(row[0], row[1])
 
     @classmethod
     def all(cls, db_conn: DatabaseConnection,
 
     def save(self, db_conn: DatabaseConnection):
         """Add (or re-write) self to database."""
-        db_conn.exec('REPLACE INTO days VALUES (?)', (self.date,))
+        db_conn.exec('REPLACE INTO days VALUES (?, ?)',
+                     (self.date, self.comment))
 
                          [day1, day2])
         self.assertEqual(Day.all(self.db_conn, ('2024-01-03, 2024-01-01')),
                          [])
+
+    def test_Day_comment(self):
+        """Test Day.by_date()."""
+        self.assertEqual(None, Day.by_date(self.db_conn, '2024-01-01'))
+        d1 = Day('2024-01-01')
+        d1.save(self.db_conn)
+        day_retrieved = Day.by_date(self.db_conn, d1.date)
+        self.assertEqual(day_retrieved.comment, '')
+        d2 = Day('2024-01-02', 'foo')
+        d2.save(self.db_conn)
+        day_retrieved = Day.by_date(self.db_conn, d2.date)
+        self.assertEqual(day_retrieved.comment, 'foo')