Redundancy is key. There should always be two methods for calculating a child's ANNS (Aggregate Naughty Nice Score). I propose a conventional method where activities are graded from -5 to +5 where a child's ANNS is the sum of all their previous activities, this would be a child's historical ANNS. And I propose a second system where only the activities performed within the last 365 days of calculation are considered, to account for children who have drastically changed behavior year to year, this would be a child's current year ANNS. I think the current year ANNS would hold more weight in Santa's judgement but looking at the historical ANNS in conjunction with the current year could help provide a better picture of a child's character.