Yearly rankings are the aggregated standings from subsets of matches within the group, including all matches played during a calendar year.
Now is the time to draw up a balance of the year that just ended! The 2018 subset (and the subsets for all previous years, if any) will be built and processed for all Plus groups (both existing and future upgrades) in a few days, as soon as a sizable number of match is recorded in 2019. And the 2019 subset will be built at the same time!
Of course, each subset has its own ranking, graph, and stats (check 'Games and subsets' widget for available subsets).
Therefore, we suggest you keep recording your matches in your original group, so that you can keep collecting statistical data, enjoying your new year ranking without losing the global ranking (with all-time stats, belts, badges, activites). Both rankings (global and yearly) will be updated after every match. You can easily switch rankings in all widgets.
Also, please remember that admins can always edit or delete previously recorded matches (adding, removing, or exchanging players, changing parameters, etc).
Happy gaming, and happy new year!