From ICS File Viewer:
ICS File Viewer is a simple web service to view and convert ICS files. Convert to loads of formats including CSV, XLSX, PDF, HTML, JSON & XML. ICS files are used to store calendar information. Whenever you export a calendar from Google Calendar, Outlook, Lotus Notes or any other calendar provider they usually save it as an iCalendar (.ics) file. These files are not very easy to read so use our service to get your calendar into a spreadsheet (.xlsx, .csv) or view it directly (.txt, .html, .pdf) to see what's going on.