Dismal used to be a date. Medieval calendars marked two unlucky days in every month, twenty-four in a year, and called them the dies mali, the evil days, which reached English through Anglo-French as dismal. You could look one up in advance and decide not to start a journey on it. Nobody was quite sure why those days were bad. They were also called Egyptian days, and some put them down to Egyptian astrologers, others to anniversaries of the plagues of Egypt. In time the calendar fell away and only the mood stayed, so a dismal day is now something you find out about when you open the curtains. The word began as a forecast you could read ahead of time and ended up as weather you can only report.