The 255 char limit can be problematic sometimes with opening hours. But only with the really crazy once. There is even a shorter and by todays spec perfectly valid way to express this:
Jan 31,Mar 01 -1 day,Mar 31,Apr 30,May 31,Jun 30,Jul 31,Aug 31,Sep 30,Oct 31,Nov 30,Dec 31 off
It just combines the way I had expressed it previously and includes the fix from SimonPoole for Feb. Thanks also for your thoughts, muralito. You got me thinking about the “Jan 31” part again. This brings us down to 94 chars and leaves 161 chars for other use which should be a practical option which is specified today. https://openingh.ypid.de/evaluation_tool/ does not support it yet but that is not important here.
Edit: Thanks to SimonPoole for the hint.