How to convert OLM to ICS data for Mac OS? To solve this problem, I think you should try to go with the powerful Mac OLM Converter Tool which can easily batch convert OLM to ICS data for Mac OS without losing any information. The program can convert all emails, calendars, contacts, notes, tasks, etc. Also, it is a Mac-supported program that can be accessed on any latest and below edition to convert OLM to ICS data for Mac. To get more info about the program, try its free demo version.