what was serenity's timeline?

Be in some amber-> Get freed from amber-> Chill with WV for about a year years-> Jump up on the sleepwalking Roxy’s head and go for a ride-> Enter the game with the Alpha kids-> Descend on down in the Act 6 finale. 

This might be different considering the Retcon. And yes I know they were on the meteor for 3 years, but they were only at the 1 year mark when they ran into Roxy and BG!Dirk