The Whole Weeks Calendar is a leap week calendar designed such that each period within it contains a fixed number of 7-day weeks. The basic calendar is the Symmetry 4-5-4 Calendar, with months of 28-35-28 days in each common quarter. But the leap week is placed according to McClenon's 5:40:400 leap week rules, with a leap week placed at the end of every fifth year, except for each 40th year not divisible by 400. While this is astronomically jittery, it forms a very systematic hierarchy of years, all of whole weeks at consistent, memorable intervals. The epoch of the calendar is Monday, January 1, 1 CE of the Gregorian Proleptic Calendar .