Mavericks Calendar info: NEW data being replaced by OLD

After upgrading to Mavericks, and then learning that iCloud is the only way to now sync Calendar info between devices, I am trying to play along. BUT, the NEWER data in my Mac Calendar is being replaced by OLDER data that somehow lives on iCloud. I had never knowingly signed up for iCloud, and in fact had been purposely avoiding doing so. But since I rely on synching my iPhone and Mac calendars, I figured I now have no choice. But I cannot figure out why the newer info is being overwritten by the older. I have searched a variety of forum threads and Apple help topics, including these http://support.apple.com/kb/TS4337 and http://support.apple.com/kb/ht4968 to no avail.

While plenty of people are having plenty of problems with the new iCloud-mandadory sync, I have not found anyone mentioning the specific problem of old info replacing new. Has anyone else encountered this? Anyone found a fix?