IIRC, the 28 day month was the norm before the introduction of the Gregorian calendar, and it is still used, for example in the Islamic calendar (that's the rea

IIRC, the 28 day month was the norm before the introduction of the Gregorian calendar, and it is still used, for example in the Islamic calendar (that's the reason why the fasting month of Ramadan drifts from one year to the next).