Recycle Your Calendars!

Have you ever had a beautiful calendar, and been disappointed when the year was over and you had to throw it away? You don't need to ever do it again! Although a calendar for one year cannot be reused the following year (since the dates of the month will necessarily fall on different days of the week), it can usually be used in a subsequent year, when the dates of the month once more line up on the same days of the weeks. Due to the occurence of an extra day in February more or less every four years in the Gregorian Calendar, the pattern of repetitions is not as regular as one would like, but it's there nevertheless. Use the following table to find out when you can reuse your calendars:

Partial Recycling

Can't wait that long? Really liked that 2000 Swimsuit calendar and don't want to wait until 2017 when you're too old to enjoy it? Recycle partially! If January 1 of a year falls on the same day as January 1 of your favorite calendar, you can at least reuse the first two months (you may have to write in or scratch out February 29). If March 1 of a year falls on the same day as March 1 of your favorite calendar, you can reuse the last 10 months! The following tables show the years which share dates in this manner. Find the year of the calendar you have, and it can be used for the first two or last ten months of any other year in the same row.

Minimal Sets

Obviously you need at least seven calendars before you can stop buying. But which seven? For example, the calendars 2000-2006 would leave you short on years beginning on Friday, or whose March 1 fell on a Sunday. The lowest minimal set I could find is:

   2001 2002 2003 2005 2006 2009 2010

The lowest minimal set starting with the current year (2005) is:

    2005 2006 2007 2009 2010 2013 2014

Richard Hoffman / ubiquity@yahoo.com