pfSense

Page: https://docs.netgate.com/pfsense/en/latest/firewall/time-based-rules.html

Feedback:

I don't know if anyone fixed this - but I'm just typing this for anyone who might need it as I did, and I solved it with javascript.
I wrote a small bookmarklet in javascript that selects all days in the current month.
It can be expanded to select the whole year at once. As far as I care - they can even integrate it in the main interface, for easier management of the schedule dates...

Here it is:

https://jsfiddle.net/lovetruth/bdLnhw3m/2/

and the code inside the js section can be transformed easily into a bookmarklet using this site:

https://www.yourjs.com/bookmarklet/

And then you just drag and drop your converted blue bookmarklet into your bookmarks bar and use it whenever you have the calendar of the firewall schedules in front of you.

Success!...