Piwik says no visits but piwik_log_visit has 2m entries

I wonder if anyone can make sense of this

Last week I had one day where Piwik says there were no visits. I knew that wasn’t true so I ran
`SELECT COUNT(*) FROM piwik_log_visit WHERE visit_last_action_time > ‘2016-03-04 00:00:00’ AND visit_last_action_time < ‘2016-03-05 00:00:00’

Which`of course gave me the 2m entries I was expecting. Why is that day missing from Piwik reports and what can be done?

Dates in the DB are in UTC timezone. Keep that in mind.

Regarding your issue, I’d suggest invalidating archives for this day and rearchiving. See this one: How do I record tracking data in the past, and tell Piwik to invalidate and re-process the past reports? - Analytics Platform - Matomo

Additionally, please check the archiving logs. Maybe there was some issue, e.g. memory_limit.

My local TZ is UTC too so that is moot. I have just run the invalidation and what I am seeing is very curious. No pageviews or visitors for that day but all the Events have been tracked. How might that be possible?

Could you check the logs of the archiving process?

You can also reprocess the data for that missing day: How do I force the reports to be re-processed from the logs? - Analytics Platform - Matomo