hum.... happen_time is a column of db.cash_journal ? and you want only the records that satisfy the conditions on the query, and in addition, that the difference in seconds between happen_time and now is less than "seconds" (259200) ?
Without a test db I can't confirm, but can you try something along the way of (db.cash_journal.happen_time.seconds() < time.mktime(now.timetuple()) - seconds) ?
