This is my first try ever to contribute anything in elisp. The nextcloud calendar app supports the X-PUBLISHED-TTL option if subscribing to an ics file. Nextcloud defaults to a TTL of 1 week, what is much too long for my use case. When exporting to such a file from org I did not find any way to set this option during export. So I tried to add a defcustom in ox-icalendar.el. The default TTL in this patch is 1 hour. I think this qualifies as an tiny patch, as it is mostly a docstring :-), in case anybody finds this an useful addition. The patch is relative to 9.5.1 from elpa. All comments very much appreciated. And a happy new year to you all Detlef