Hi txd1956, I don't use a Mac, I'm using using Thunderbird 38.1.0 on Windows 7 (x64). However, I know that Lightning can import iCalender (*.ics) files. Export your Mac calendars (https://support.apple.com/kb/PH11524?locale=en_US). Then open the Lightning calendaring tab and click on "Events and Tasks" and then click on "Import". You will be given a choice of importing, at the least, iCalendar *.ics files, or CSV files. Choose iCalender for the type of file and navigate to where you exported your Mac calendar files. Hope this helps, Norio