n. 1. An unspecified but usually well-understood time, often used in conjunction with a later time T+1.
"We'll meet on campus at time T or at Louie's at time T+1" means, in the context of going out for dinner:
"We can meet on campus and go to Louie's, or we can meet at Louie's itself a bit later." (Louie's is a Chinese restaurant in Palo Alto that is a favorite with hackers.)
Had the number 30 been used instead of the number 1, it would have implied that the travel time from campus to Louie's is 30 minutes; whatever time T is (and that hasn't been decided on yet), you can meet half an hour later at Louie's than you could on campus and end up eating at the same time.
See also since time T equals minus infinity.