Almost every situation in history of 1 0 1 is considered a recession but 2011, but that one wasn't considered one because Obama was president. however, every time that I know of, back to back shrinking quarters has always been a recession, as far as I know.
And it matches up, we all know its a recession now (except those who want to deny its one because of their political view). its a recession, you only look more wrong trying to deny the obvious.
Only two though-- Q2 was so sharp that everything after that was recovery.
It wouldn't be unusual for a major economic calamity to occur within a single quarter. Both Covid lock downs and the collapse of AIG/LB happened within a matter of weeks.
But that's not receding, that's has receded.
If your implied definition is slipping below the growth trend, then any '50% collapse' is going to ensure 'recession' (by this definition) for probably (or even hopefully) a long time.
A recession is past tense. One can speculate that we are in a recession, but it's not feasible to collect all the information necessary to make that determination in real time. The best one can do is say, "a recession started six months ago, and I think the situation is better/the same/worse."
Shift the quarter to begin in Feb and you'd only have 1Q of decline.
That is why the 2 quarters rule is stupid and why 2020 doesn't fit the rule.
It's just a rule of thumb, not some profound maxim of economics.
That said, you can apply the same to GP's suggestion of months, if the timescales are even shorter.
Begin using the data > Section 1 Domestic Product and Income > Table 1.1.5 Gross Domestic Product > Modify > First year 2016 (refresh table)
Using the 2 quarters rule (something that has no official bearing) means that 2 of the last 3 recessions (2000 and 2020) weren't recessions.