I alluded to Matt's time-machine work back in the "Father Time-Travel" storyline (not to mention it's mentioned in the cast page as well).
TRANSCRIPTION COURTESY OF JOSEPH HOUK - [Downtown San Francisco!] (CW) "Got the hotel keys, Beth?" (BG) "Got 'em... Now, let's get to San Jose!" (CW, in front of the Merchants Exchange Building, handing Matt the time machine) "We're not gonna need the time machine for this... So here you go, Matt. Please be careful with it." (MG) "Sure thing!" (BG) "Sometimes I find it hard to believe that you can trust him with your machine." (CW) "Well, he's taken it on solo trips before, and after all, he did help me put it together... (walking away) ...I'm pretty sure he's not gonna pull anything drastic like relocate the Golden Gate Bridge! (BG looks as CW doesn't notice that the plaque outside the Merchants Exchange now reads 'Matthias Gahan Building'...) Come on, the rail station should be just a few blocks away!"