Resumen
As we approach the end of the 2nd millennium AD, it is obvious that there is much confusion as to how and why our calendar is constructed as it is. The length of a year and the astronomical age are both defined by the position of a point in the sky known as the first point of Aries. This point moves with respect to the stars and hence there is a problem in trying to synchronise astronomical events which determine the seasons with a fixed date in the calendar. The Catholic Church?s desire to celebrate Easter on a date set by certain astronomical events, led to the implementation in the 16th century of the calendar now used internationally.