A dynamic in which to succeed, one must return at a predefined time to take some action. Appointment dynamics are often deeply related to interval based reward schedules or avoidance dyanmics.
Example: In games like Happy Aquarium and Farmville, returning at a set time to feed fish or harvest crops rewards the user. Failing to return on time causes damaged crops or lost fish.
(Source: SCVNGR Playdeck)
Failing to return to FarmVille on time causes pants to wither: