The issue was always about how to bring the two major calendar driving events into sync, the sun and the moon. The most common Kludge was to make months 30 days long which came close to the lunar cycle and then throw in some arbitary number of non-counted days to synch up with the solar calendar. The would add the days as a bunch at the end or beginning of a year or place them a few at a time between months.
Of course, since neither the lunar or solar cycle work out to be a number that can evenly be divided, none of the calendars worked well over time. They all got out of kilter and so you needed a special class of people to keep track and fudge the final figures every year. They called them Priests.
Aslan is not a Tame Lion