Record Have Been Changed After Replay After A Couple of Days

I found some sleep cycle graph differences on last day. Once, I woke up, I found the sleep durating short and example end time is 4:30 AM. Next day, I look back though that day, wake up time is 5 AM. Why record is

changing per day even the sleep cycle graph have to stay the same as record replay back.

  • Which watch model? At older models the sleep analysis happens on Garmin's servers, after you have synced your night data. You first get some raw estimate, but the data is then processed deeper, and the results are finetuned, so it can indeed happen that the stats change during the day.

    On newer modes it is rarer, but it can still happen, because the night data is being compared with the day data, and some adjustments can happen. More on it in the FAQ: Viewing Sleep Statistics and Details in Garmin Connect | Garmin Customer Support

  • Vivoactive 6, first day check the sleep cycle after woke up and it is end on (Actual wake up) 4:47 AM correctly. I took snap on Garmin Connect website. Next day, look through back record, it is getting 5:00 AM with light sleep state(seem sleep duration setting until 5:00 AM). It may adjust upon setting eventhough actual wake up time is define at that day. I just a little suprise on that and reducing my trust on this sleep cycle records. 

  • Thanks-this makes sense now. My Vivoactive 6 also showed a sleep time shifting later the next day. Good to know it’s due to server-side analysis to refine your data post-sync.