Why did the Gregorian calendar reform happen at all ? Was it necessary ?
A. The calendar reform established by Pope Gregory XIII was necessary because the Julian calendar used in those days had begun to lag behind astronomical reality – which is to say that by the time 21 March came around on the calendar, the actual, astronomical vernal equinox had already happened. The fundamental problem behind this is that the astronomical year – that is, the time the earth takes to make its journey round the sun – is not exactly 365 days: it’s actually 365 days, five hours, 48 minutes and 46 seconds. However, as the year has to be divided into equal portions for practical purposes, leap years have to be introduced to resolve the problem.
