That's true, they are happening 3 years apart, but I'm having a hard time working out the sequence of events without breaking the space-time continuum, LOL.
They blew up Jughead in 1977 and were thrown forward in time to 2007, which is where the current island activity is occurring.
In doing so, the "it worked" that Juliet mentioned caused the plane to land in LA in 2004 with different fates - Hurley's a lucky man in 2004 because, with the island at the bottom of the sea after the explosion, the numbers are no longer bad luck to him, for example.
But at some point, they have to get to the island in order to have the 2007 events occur (Locke has to die so MIB can assume his identity and kill Jacob). For that matter, they have to get to the island in order to skip through time, get back to 1977, and blow up Jughead.
And that's about the time that my head explodes and I just wait for the next episode.