Did the U.S. Recession Start in February or March?

Some seem to think that the NBER declared a February recession start. It did not; rather, it declared a February cyclical peak.

So when did the recession start? It's a bit ambiguous, since a peak is an apex atop both the upward expansion path and the downward contraction path. Indeed the NBER's press release states that "The [February 2020] peak marks the end of the expansion that began in June 2009 and the beginning of a recession."

Nevertheless, when measuring expansion and contraction durations, the NBER convention is that peak months are taken as part of expansions ("the last month of good times"), and trough months are taken as part of contractions ("the last month of bad times"), as in the NBER table here.