I have a couple of users with an issue with their calendar's Month view.
They have several shared calendars that they normally see. Every once in a while all of the the appointments disappear from the month view. If you click on week or day, the appointments are still there. Click back on Month and they do not show. If I right click on Month and select properties and change the month view from the currently selected one. The appointments show back up. But later one down the road the appointments disappear and we have to select yet another view and they return.
Sometimes reboots work and the appointments come back sometimes they can reboot multiple times and still no appointments show up. I have not hear of this issue with everyone just a couple of users. They are using the 12.0.2 client. I believe build number 108211