Most of the achievements can be earned year-round. If you open the app on your phone, head over to the Achievements tab, you’ll see some of them listed even before you earn them (in which case they will be represented by a blacked out version of the award).
However, there are some achievements that are not shown until you earn them. Past and future monthly challenges, for example, won’t show up, nor do all the various individual exercise workouts.
2021 New Year Award
Move Streak Award