There were close to 5000 entries (more than there should have been because some were duplicated by accident as well as some entries from 1947???). The good ones dated back to 1997 which is when I got my Newton. I replaced the Newton in 1999 with a Palm and then replaced that a few years ago with a Sony Clie.
My solution was to export them from the Mac Palm Desktop as a tab marked file - that's the only thing in common with FilemakerPro into which I imported them. I created an extra field called keep, created a button to set it and scrolled through the entire listing clicking on the ones I wanted to keep.
I then exported them from FMP to a tab marked file and reimported them into a new calendar in the Palm Desktop. Then the plan was to export them in vCal format and import them into iCal - vCal being the only common format. Apparently I'd messed up the original import into FMP so that the dates were not dates but text. It took several tries but I was able to construct a proper date text field in FMP which included translating the month names back to month numbers. There was also a problem that the original export only had past items so I had to reenter all the future ones manually, but that was OK because of the completely different convention about labeling different categories of events in iCal vs. the Palm Desktop. And then it was an easy synch to get them into the phone.
I see in the folder that I used for temporary files that there are 13 of them resulting from the various abortive attempts. I did look around to see if there were any free tools that would help and that wasted a bit of time.
I still have to decide if I actually like the phone or not. I had to reboot twice when deep into Internet Explorer, but that is what I kind of expected from WindowMobile.