I have Yosemite 10.10.1, after the upgrade my Cal has a 1 in a red dot on it, like there is message or something. What is this?
Go to help topics and the answer is there. It happens when someone invites you to an event and you have not accepted yet. In the top left corner of the calendar screen there is a symbol that looks like a u with an arrow pointing downward, Click on this and the events appear asking if you want to accept or decline. one you complete the number disappears.