The calendar does a lot more than tell you the days of the week - it helps you keep track of reminders and appointments. Select Menu, Organizer, and Calendar. While in calendar view, simply scroll to the day for which you wish to make a note, press Options, and Make a note.

You have the option of entering a Meeting, Call, Birthday, Memo, or Reminder. Each of these can be set with an alarm if you wish, with or without sound, from 5 minutes before the event to 7 days before.

Try a simulation of the calendar by clicking here.