That old 2015 calendar? You can re-use it in 2026! You will have to wait until 2044 to re-use your 2016 calendar. But you can re-use a 2017 calendar in 2023 and your 2018 calendar will be good for 2029. (Of course, there’s a When can I reuse this calendar? website.)
If you save a calendar every year, eventually you won’t have to buy any. Often you can re-use a calendar for a given year 11 years later, though sometimes it’s only 6 years later, and sometimes it’s 12, or it could be more.
Why can calendars be re-used? Because there are only 14 different calendars.
There would only be 7 different calendars, like this:
- the first day of the year is a Sunday,
- or a Monday,
- or a Tuesday,
- …
except for the extra day on February 29 that usually occurs once every 4 years. Given the more-or-less quadrennial extra day, there are actually 14 different calendars:
- the year starts on a Sunday and doesn’t have an extra day,
- the year starts on a Sunday and has an extra day,
- the year starts on a Monday and doesn’t have an extra day,
- the year starts on a Monday and has an extra day
- …
Once you collect all 14, you’re ready to stop buying calendars!
For more information:
& (the answer)
http://whencanireusethiscalendar.com/
http://www.hermetic.ch/cal_sw/idcal/idcal.htm
