HT4993 I used and have used my yahoo email and that email address for my calendar and suddenly dates are disappearing why?

Question

Dates in my calendar have disappeared?

Answer 1

The path may be long and tedious, grasshopper.
Actually, the download of Office 2011 for Mac probably was not legal and may have contained bugs or other things meant to make it unstable, or invite a host of issues. The usual path would be Office 2011 for Mac on DVD so you could reinstall it and add the extras from the disc as needed; or fix the installation later on. The updates for security were downloads from Microsoft servers. You'd need a legitmate version with pass code.
Options for Mac and office-like application suites include Libre Office, NeoOffice, and these run free. The latter supports up to Mavericks. 10.9.1 now. They have a word, excel, and other parts a lot like the real office.
If you have a working clone of the system prior to installing the Office 2011 for Mac download and any subsequent and perhaps unseen extras, you could revert to it simply by restarting the computer from the clone, where it resides in externally enclosed self-powered hard disk drive, of a type known to support OS X clones... With ports to help work with most modern Macs. FireWire + USB. Then, clone it back w/ carbon copy cloner.
Short of that, perhaps someone will see your post and offer some indepth method of hunting down bugs via use of Console logs; and maybe booting into Terminal utility to use unix code. It can be rather involved. Maybe Linc Davis will offer some detailed reply that will invite you to read carefully and try it.
I've given up using computers long ago.
A pet raven has been taught to write this.
Good luck & happy computing!