Actually I hadn't noticed but the JS evaluation_tool shouts loudly when using no separator. It does the intended thing, but it says the syntax is incorrect.

And AFAICS it's not a bug (that a comma won't do the right thing), the spec says
"Note that an additional rule does not use any data from previous or from following rules. "

So the only way to write this correctly is to repeat the whole wide range selector:

May 01-Jun 15,Sep 01-30 Mo-Fr 10:00-18:00; May 01-Jun 15,Sep 01-30 Sa-Su 09:00-19:00; Jun 16-Aug 31 09:00-20:00

OK with you if I change it to that?

This is also indirectly explained in
https://github.com/opening-hours/opening_hours.js#todo
which says "List of [possible future] features which can make writing easier:
May-Aug: (Mo-Th 9:00-20:00; Fr 11:00-22:00; Sa-Su 11:00-20:00)
". This syntax does not exist, but the fact that it's described there proves that there is no current way of making a month range apply to a number of rules.

Thanks for making me realize all this.

Oh. I see. Wow. Very unexpected. I'll research this further and come back to you.

Hello. The "Sa-Su 09:00-19:00" is supposed to be only during the time frame "May 01-Jun 15,Sep 01-30"? Then indeed both of our versions were wrong, a comma should be used. A space was incorrect, and semicolon means it's always open Sa-Su which seems unlikely. Sorry for not catching this wrong autocorrect. I'll fix the value with a comma.

But actually, any good suggestion for the changeset source? The spec (osm.wiki/Key:opening_hours) ? The software (https://github.com/dfaure/OpeningHoursFixer) ? Or "extrapolation" ?

Oops, you are completely right. This is a side effect of osm-bulk-upload/upload.py which defaults to survey if the -y argument isn't specified. I just submitted https://github.com/grigory-rechistov/osm-bulk-upload/issues/2 to signal this problem, and I'll fix my script.

Hello,
I had documented this edit at osm.wiki/Automated_edits/davidfaure_bot

Should this rather be in Mechanical_Edits? It's 90% automated, 10% manual since I review all changes before submitting them.

This edit is based on the findings of the Osmose plugin for invalid opening hours - which I contributed myself, https://github.com/osm-fr/osmose-backend/pull/1051
I was initially doing those edits in osmose, then I wrote a more convenient GUI for reviewing those changes, but the idea is exactly the same.

It is strange that I didn't get notifications for all the messages addressed to davidfaure_bot since I did get notification for two of them (the two I replied to). I shall reply to the others now.