[Svartalfiar]

The Senate does not go into recess. Every three days, a Senator opens a pro forma session of the Senate and then immediately closes it. For whatever reason, three days has become the norm to determine how long the Senate can be not in session and not considered in recess.

Three days is the norm, because that's the time needed for either side of Congress to get permission from the other to go into a longer recess. So basically, one, two, or three days off is simply considered a weekend, whereas four or ore days with Congress not meeting is technically considered a recess.

But, a single Senator shouldn't be able to conduct a 'pro forma' meeting of the Senate, as the Constitution requires a majority of Senators to be present in order to conduct business. so if the 51 person quorum isn't met, then the recess-blocking isn't a valid meeting of the Senate. Pro forma means it's an official meeting, they just aren't really doing anything. If they don't have the quorum, then they're not actually in session. (No clue if SCOTUS clarified this in their Obama ruling or not. Or if it was even an argument made.)

[Dave W]

Thanks for your interesting reply. As far as the quorum requirement, I wonder if it has anything to do with someone needing to request a quorum count and if there is no one there to request a count, then technically it is a session? I’m just guessing.