What if you hadn't of know beforehand that the 31st was the _only_ one that missed out?

Then I would never have given the matter a single thought.

But ... consider this: someone finds a curious phenomenon and reports it to his fellow scientists. These start running a number of experiments which prove or disprove this phenomenon in a variety of circumstances. Then someone steps in and formulates a theory and finally someone proves (based upon the existing body of scientific knowledge) that the theory is correct.

I think we just have witnessed the scientific method at work in our Monastery!

Don't you mean February?

No no, I really mean January. February never has 31 days, so by starting my "year" in March (as did the old Romans -- why do you think September really means the seventh month?) my reasoning does not have to take into account leap years but for the month of January (which as lidden said can only be a "+5" of "+6" day but never a "+3".) thus making my proof much easier and clearer.

Shall we --in line with good scientific practice and hubris-- call this theory the "McDarren-CountZero-lidden Theory of the Missing Weekday of the 31st"?