Problems with converted ics file

Since Apple no longer supports my Palm TX I have had no way to sync my PDA. I had a chance to upload my old 10.6 OS on a computer that had been reformatted so I could use it to retrieve my old data bases. I'm working at getting the Palm calendar, which covers about 13 years of info, into a format that my OS 10.8.5 will be able to read. I used a program that converted the .pdb file to a .ics file that should be readable by Calendar 6.0, but of course it doesn't. I have been looking for solutions for about 6 hours now and it's driving me nuts. I did read a post that was about 3 years in length dealing with a similar problem and tried using TextEdior to try some changes, but nothing works. When I try to import the file I just get, "Calendar can't read this calendar file. No events have been added to your calendar." I even tried downloading a totally different calendar and that didn't work out either. What format file does Calendar 6.0 use? It's obvious from what I have been reading that .ics files are a problem. Any suggestions? Thanks for your help.