One's Got Class and the Other One Dyes - S3-E4
Continuity mistake: When Lane and the band are arguing in the music shop and Dave ushers Lane to go outside to talk, she picks up her jacket on the way out the door. When she gets outside, though, she has no jacket. (00:09:00)
Chosen answer: Lorelai and Christopher get married impulsively in Paris but they get divorced shortly after returning home. I don't know the exact number of days or weeks but they definitely weren't married for more than a couple of months.