Some number of updates back, the calendar app no longer accepts our custom holiday .ics URL (Admin / Apps / Calendar / App Configuration / Custom URL for iCal with holidays for all users). I noticed this because we see nearly every day marked as a holiday, presumably because we are using the US Mozilla default.

The calendar app config page will blank out the custom URL field. I can add back our custom one, then press Apply on the page. From the logs on the web server hosting the custom URL, I see the HTTP GET for the .ics file with no error, but egw reports the error in the subject line of this posting. I think this probably means it’s not a transport issue but a file content issue.

I’ve tried self-hosting the Mozilla US holiday calendar, and a truncated version with no calendar events. Both experience the same problem described above, that is I can see the egw server requesting the .ics file successfully, but it reports “Error: Invalid iCalendar URL”.

Here’s the empty file contents I tried, for reference:

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Mozilla.org/NONSGML Mozilla Calendar V1.1//EN
END:VCALENDAR

Does anyone have a suggestion on how I can better troubleshoot this issue, or see an obvious problem in the ‘empty’ .ics file content above?

Thanks,
Steve