### Recycling Calendars

2009 is almost here, and that means a new calendar. Or, you can just recycle an old calendar. If you think about it, only 14 different calendars exist. January 1 can occur on any of seven days -- but some years are leap years and have an additional day.

Assume column A contains years, (beginning with 1901) and row 1 contains the same list of years, arranged horizontally. Put this formula in cell B2, copy it down and across:

```=IF(AND(WEEKDAY(DATE(B\$1,1,1))=WEEKDAY(DATE(\$A2,1,1)),DATE(B\$1,12,31)-DATE(B\$1,1,1)=
DATE(\$A2,12,31)-DATE(\$A2,1,1)),"X","")
```

The cells that display an X indicate matching calendar years. For example, the 1901 calendar is identical to the 1907 calendar.

If you use conditional formatting to highlight the cells that contain an X, it makes an interesting pattern:

If you don't want to go through the trouble of creating a worksheet, you can use any of the following calendars for a 2009 calendar: 1903, 1914, 1925, 1931, 1942, 1953, 1959, 1970, 1981, 1987, or 1998.

By the way, if you start saving calendars in 2009, you will have a complete set of 14 different calendars in 2036.

Permalink | Posted in General on 28 December, 2008 2:37pm