In that same episode, Dan talks to Frank as Frank is about to go take pictures of President Ford. As a result of this delay, Frank is not there when Ford gets shot (although the assassination attempt was in Sacramento, about a 1.5 hour drive from San Francisco). Frank says something like "thanks a lot" (sarcastically) because Dan made him miss it.
Elliot Langley, the apparent time travel scientist, claims to have known Dan's father, Frank. It is still not clear why Frank left his family. Did Frank get knocked out of the "normal" timeline by this change of his past by this future version of his son, and become a time traveler himself?