Q: when i upgrade

Macintosh4579 wrote:

 

when i upgrade to mac os 10.10 will all my events on my calendar come to 10.10,

Why would you want to do that?

OS X 10.10 Yosemite has not been released by Apple and no one will be able to answer that question until it is released.

Not only can no one answer such questions until release, rules of this board strictly forbid speculation.

Until it is released, how the Calendar behaves will be completely an unknown, just as how any third party calendar program does as well under

the new operating system.  In spite of the fact that http://www.roaringapps.com/ has reports of "compatibility" with 10.10, all those reports should be taken with a LARGE grain of salt until the actual release happens.   Apple may tweak things that break certain programs between now and then.   Watch http://www.apple.com/osx/ and http://www.apple.com/pr/ for updates. 

If you are running Tiger, which this forum covers, you cannot upgrade to OS 10.10.

Klaus,

No one knows that definitively.   Some Tiger people can upgrade to Mavericks:

Are there 10.4 systems that can upgrade to 10.8 or 10.9?

It stands to reason if 10.10 is not too different from 10.9 they will also be able to upgrade to it, but as speculation is forbidden, and people testing it are under non-disclosure, there is no way of knowing for certain.