Last Accessed date is not accurate in SharePoint site

Hello All,

We are planning to decommission a sharepoint site. We know that nobody is using the site or accessed the site for past 2 years, but when we ran an analytic report (either using tool or PowerShell script), it shows last accessed 5 days back which is not the actual date. I am suspecting its a system change something happening internally. So this is really a challenge for us to decide whether to decommission the site or keep it. How to know if the site is modified by the actual user or it's just a system doing.

Please suggest some smart approaches.

Thanks.

Knowledge is power.