A Waltz Through Time

An accident with a time-turner in the summer of 1971 sends Severus Snape and Lily Evans 20 years into the future. With their time-turner destroyed, and no way back to the past, they befriend Harry Potter and try to make a life for themselves in a time where they do not belong. And how do Ron, Hermione, Dumbledore and present-day Snape factor into all of this? AU, Canon-divergence.