Nathan points to a handy cheat-sheet of commands you can use at Ask.com.
geoloc: (insert code) – searches one geographic location:CA(Central America),EU(Europe),IA (India or Asia),NA(North America),OC(Oceania),SA (South America)
last: – last date modified; i.e., last:week, last:month, last:year
beforedate: – (insert specific date); i.e., search engines beforedate:19880318 (march 18, 1988)
after: – (insert specific date) afterdate:19880318