Almost the best.
I wish I could give it 5 stars, but its not fully compatible with the app for iPhones. I mean, when I add something on iPad I can synchronize it with iPhone and I have that event there as well, but when I delete something on iPad, its still on iPhone... Synchronizing doesnt help.
Czapkowsky about
Calendars 5 by Readdle, v5.6.4