Q: Calendar icon messed up

Try the suggestion on this thread >  How do I restore the default icons on...: Apple Support Communities

Clarification question - is it correct in your Applications folder/can you change it there? If so, drag the icon out of the Dock and then drag it back to the Dock from your Applications folder.

Hi Emily,

I'm not sure if you're still having this problem, but I recently tried the whole custom icon thing and then reverted back, but my calendar did not change back.  It was correct in the Finder Applications folder, but Launchpad and Dock were stuck with the custom icon even after every other icon reverted back.  I found out how to fix it.  Within the package contents for the calendar, there is another folder called calendar.docktileplugin.  Within this sub folder is another resources folder.  Within that is the app-empty.icns file that is required to make the icon on the dock work.  Mine still had the old custom icon in it.  I had accidently deleted the original, but from within the resources folder above I simply copied that app-empty.icns file and pasted it into the resources folder of the calendar.docktileplugin folder.  Hopefully, you didn't get too lost.  After removing the app from the dock and re-adding it, it is now correct for me.  Hopefully, this will work for you as well.

BTW I sort of reverse-engineered this from the following link.  http://www.tekrevue.com/tip/custom-icons-os-x/2/