Hi @manoj kumar, 

Thank you for writing this post - happy to assist!

I understand you are asking why Active users data for past days changed, correct? Historical data could change when there is data backfill. Data backfill can happen for different reasons depending on how you ingest data into Amplitude. 

For example, if you are using our SDKs for ingesting data. To begin with, our SDK’s have built-in batching that only uploads events after 30 seconds or 30 events. If a user opens the app, but quits within 30 seconds, our SDK will not have enough time to upload the events. We attempt to upload events when the app enters the background, but if the upload takes too long the OS might just terminate the app without letting it finish, so there’s no guarantee it will succeed. Events that are not uploaded will be stored locally or in the cookie. 

Another reason I can think of is losing internet connection during the session. Then events fired will be stored locally and uploaded at a later time. 

One way to verify this is to find an example user that made the number change, and check the events one the day of change. The events on that day must have a difference between Client event time and Server upload time, as shown on the example screenshot (this is not from your org, but a general example). User/event is counted on the day of client event time (May 26), even though they are uploaded to Amplitude on Jun 3. 

I hope this clarifies!

Best, 

 

Thanks a Lot @Yuanyuan Zhang