Mozilla Sunbird

Files
Where is my Calendar file?

By default local calendars are stored in a sqlite database file called "storage.sdb". This file is located in your profile folder. (LINK ME)

Network calendars can be stored on WebDAV, CalDAV, and ftp servers and also locally (in this case "Network calendar" just indicates that the iCalendar format is used and not a sqlite database). To find the file, right click on the Calendar in question in the Calendars section. Select "Properties". The file name and path are shown in the label next to "Location".

https://wiki.mozilla.org/Calendar:FAQ#Where_is_my_Calendar_file.3F