The 53-week calendar reference article from the English Wikipedia on 24-Apr-2004 (provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

53-week calendar

The 53-week calendar is a variation of the Gregorian calendar that is used (mainly) in government and business for fiscal years, as well as in timekeeping. In this calendar, the year does not necessarily end on a specific day (e.g., January 31 or December 31). The year does, however, end on a day of the week (e.g., the last Friday in December). Therefore, weeks and months of equal length are allowed to exist. A year can have a total of 371 days.

The ISO week is an example of such a calendar.

Advantages

• There are no variations between day of week between years for a specific date.
• The calendar starts on the same day and week every year.
• Unlike the regular calendar, the there no varations of years.
• The are no fragments of partial weeks at the end of the year.

Disadvantages

• The years is not in sync to the 365 1/4 day solar year