change Mac calendar

That's what I did. I went to the Contacts page for Joe Blow, and there is nothing about birthdays there. I guess someone else has that event posted, but how am I supposed to find it? That is, how does one track an event notification back to its source?

OK, I figured it out. On the left hand side of the Calendar, there are check boxes for which library contributes to the calendar. You just keep unchecking them until the event goes away. This event was in Google Contacts, which means that Joe Blow actually did it in his Google accpunt, probably as a anonymous response to a birthday question. I'll get him to remove it.