I use iCal on my iMac, iPhone 5 and iPad mini. It works fine on the devices but on my iMac is is almost unusable . . . I believe this started when I updated to Yosemite but I'm not sure. Every time I try to make an entry i get the dreaded spinning wheel. So I pick up my device, make the entry and it syncs quickly. I have tried to research this and found older posts and other sites. I deleted all recurring calendar entries. I found older posts about plists and deleting iCal cache but couldn't even follow those directions as they were several years old and maybe things are different in Yosemite. Any help would be appreciated -it's driving me crazy!