When does plugin update stats?

When I first installed the plugin, I thought it updated the stats daily at midnight.

My writers use the icon on the dashboard in the listing of posts to get their stats. It used to update every night.

However, I’ve had some writers tell me that they get up-to-the-minute stats which suddenly stopped then went back to once a day.

Was there an update or something that changed?

How often are stats updated using the Analytics Icon on the posts page?