Synchronization with an Android phone over Exchange Active Sync (EAS) is working for emails and contacts but not calendar entries.
This seems to be a common problem with all kind of phones, versions and EAS servers.
First delete the EAS email profile on the phone, after that you have to delete the calendar cache:
Settings -> Applications
Select the "All Applications" tab
Search for the calendar and select it
Scroll down and select "delete cache"
Recreate the profile