28 Year Cycle

Years normally follow a 28-year cycle, since there are seven days in a week and leap year occurs every four years; a calendar from 28 years ago is the same as this year's (a year like 1900, non-leap though divisible by four, breaks the pattern).

The planet Saturn revolves around the Sun in approximately 28 years. This is acknowledged in Astrology and in cultures or religions that base partly on it (see below, other fields)

http://en.wikipedia.org/wiki/28_(number)#Astronomy