Tonight at 02:40 UTC, all Unix-based computers (including Apples running OS-X) will pass a milestone: 1.5 Gs since the beginning of time (at least as far as Unix is concerned).
Unix keeps track of time by counting the number of seconds since 1 January 1970 at midnight UTC, which (at this writing) was 1,499,962,035 seconds ago. Tonight at 21:40:00 Chicago time will be 1.5 billion seconds since that point.
If you miss this anniversary, don't worry; it'll be 2.0 Gs into the Unix time epoch on 18 May 2033 at 03:33:20 UTC. Mark your calendars now!