Come to the meet and greet anytime between 7:00 and 8:00 am and earn the "Last Cache of 2017" souvenir. Pair this with tomorrows Happy 2018 Cache (GC7G4YY) and you will earn both souvenirs!
Sign the log if you care to (not required, but, you know, when someone passes you a pen and a notebook...), which will be at the cache coordinates. If we appear to not be at the coordinates, we're inside the establishment!