Why are numbers of tracked visits changed retrospective?

[ckrapp]

Hi. I usually check the numbers of tracked visits and pageviews once per month for the past month and note them in a separate list. When I did so in the beginning of June, I noticed that the numbers for April, March and February had changed retrospective, compared with the numbers I noted previously. Some increased, some decreased, the total was different for this period. Older numbers were consistent and did not change, neither did this problem reappear in July/June. Does anybody know, why this happened? Thanks for your help!

[MatomoForumNotifications]

This issue has been mentioned on Matomo forums. There might be relevant details there:

https://forum.matomo.org/t/why-are-numbers-of-tracked-visits-changed-retrospective/46529/2

[bx80]

Hi @ckrapp, it's hard to know why the figures could have changed without more information. In normal usage, once a month has passed it's archived data should not be processed again. Did you install any new plugins? Was there any re-archiving / archive invalidation done? Did you create any new segments?

It could be that the archiving process for those months was interrupted or failed to complete for some reason and then a change triggered re-archiving which corrected the figures. (or visa-versa)

If you have logs from the archiving cronjob then it might be worth checking them to see if there are any errors being logged. You could also manually invalidate and re-archive the those months to confirm that the updated figures are correct and that there are no archiving issues.