The fourth factor is location (SCMagazineUK.com)
This is one of those articles that is a grab-bag of interesting identity management stuff.
If the fourth factor is location, we're obviously talking logical access control since with physical access control, location isn't in doubt.
For physical access control, a fourth factor might be time, i.e. your credentials only open the door at certain times of the day.
But time can also be a part of the 4th factor in logical verification if, for instance, your bank wanted to know about it if you use your bank card in the Enid, Oklahoma Wal-Mart fifteen minutes before "you" use the same card in St. Petersburg, Russia. Since you cant get from Enid to St. Petersburg in 15 minutes, there's a chance something is amiss.
As they say, read the whole thing.
See also: Biometrics in Emergencies which also touches upon the time factor in physical access control systems.
