I did an indoor cycling workout that I finished a few minutes after midnight, 1138 active calories.
Garmin Connect in the "Calories burned" section, active calories: 1422 (day 1) + 1142(day 2). I did max 5 minutes of workout on day 2 (after midnight), slept and by the time of writing this almost no activity.
My workout was recorded with Forerunner 955 connected to Tacx Flux 2 hometrainer.
I think it failed to overlap correctly the workout. It assigned general active calories to the first day and the whole workout to the 2nd day.

