dropOldGames :: GameList -> IO ()
dropOldGames games = do
    now <- getCurrentTime
    modify games $ filter (updatedInTheLast 30 now . snd)

updatedInTheLast :: Int -> UTCTime -> UTCTime -> Bool
updatedInTheLast max now t = dt < max
    where dt = floor $ toRational $ now `diffUTCTime` t