Catch-up event:
Credit to CasualSAB, but the idea is to make it so that players who weren't able to complete an event for some reason would have another chance to do so at the end of the year. So the event reward is a choice between any of the year's event rewards you didn't already claim. But the selection is account-wide and can only be made once.
Last chance/Final call event:
Take the same idea as above. Except that you can claim an event from the previous year. Basically, if you missed an event and the catch-up event (perhaps life/family/health issues, work got in the way, or anything else), there's still one more chance to get a reward from the previous year. It's still account-wide unlock and the selection can be made only once.
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