The magic numbers at the end of this explanation are the number of days of each part of the leap year cycle: 146097 days = 400 year portion of the leap year cy

The magic numbers at the end of this explanation are the number of days of each part of the leap year cycle: 146097 days = 400 year portion of the leap year cycles (including leap years during that) 36524 days = same for the 100 year portion of the leap year cycles 1461 days = 4 year cycle + 1 leap day