That was actually compensated for in the "Correcting for more frequent dates" section. The first graph of that section shows what you would expect the distribution to look like, since not all months have the same number of days.
The following graphs are based on variation from that expectation.
But the analysis did not account for the variable number of weekend/weekday days on each day of the month. I don't know how meaningful this is, but it would be worth it to inspect this separately and then weigh it in if needed.
The following graphs are based on variation from that expectation.