1. unable to remember the number of days in each month.
2. unable to sustain a long-term schedule or plan, due to a lack of stable subjective significance of the passage of time (i.e. zoomers), rather than disinterest in the desired outcome (i.e. slackers).
3. unable to remember appointments, birthdays, the current day of the week, the month or the current year, often experienced with hangover on New Year's day.
4. unable to flip the pages of a calendar.
5. the state of being perpetually anxious regarding all possible future courses of events.
6. believing that the world will end in some prophesied year, e.g. 1000, Y2K, 2012, etc.
7. Confused state wherein the dates comprising "next weekend" cannot be ascertained.
8. frequently absent without leave
You missed they party! Are you a flake or just calendrically challenged?
I'm sorry! The invitation arrived last Monday, so I thought it was NEXT weekend, instead of this one.