[cheebacheeba]

From what I've learned Id say yes they do.

Observation has showed us that animals that are effected by seperation anxiety disorder will display a gradual buildup of symptomatic behaviour when their "object" or person/persons are gone, getting progressively worse or more withdrawn/inactive as more time passes.

True, this only happens when they have said condition but it does show an ongoing awareness of the length of time.

Animals actually like to keep better routine than us humans also, in terms of feeding, sleeping and even mating times - whether or not this comes down to "instinct", part of them knows when, is when even if upon a more primal level than ourselves.