User blog comment:TotallyTinkerbell/The year ?/@comment-4984687-20140416201730

How do you know the apocalypse happened in 2050? I know on Jasper's shirt it said Earth Day 2050 but that could just be something completely different.

While it is likely it occured in 2050, it's not confirmed. In future episodes I think they'll say, maybe even the Grounders themselves can speak and explain it.