You can use the date you assign to a note as you wish. For example, if you write blog posts or daily updates, you’d probably assign the date you created the note. However, if a meeting is only next week, you’d assign that date in the future. Similarly, for some notes it’s perfectly fine to assign a date that you consider the due date (though you can also use due tags like #due(tomorrow) as an alternative). Just how you see fit.
Note that when it comes to timing and tracking, we also hope to add support for reminders in a future update of Agenda, which might also help in this area.