Often you can buy "old" calendars and diaries for almost nothing when the year is half over - stores don't want to hold onto stock and there's little chance of selling a calendar that only has a few months of useful life left.
If there were no leap years, then every calendar would be recycled on a 7-year cycle, the first day of the year moving forward by one each year (because there's an extra weekday each year: 365 mod 7 = 1). Due to leap years making non-leap year calendars incompatiable with leap-year calendars that start on the same day, the calculation of reusable calendars is a bit complicated - usually a calendar can be reused 6 or 11 years later. I've listed the reusability years for the next 10 years worth of calendars below.
Therefore, if you find you have an unused calendar at the end of the year, and you have some spare storage space, just put it aside and you can probably reuse it in 5 years time. If you're really frugal you could wait for the chance to buy calendars for 80% off, and put them aside for 5 (or more) years until you can use them. Although you'd miss out on interest on the money paid for the calendar, the price of printed items tends to go up faster than the general inflation rate, so it's a pretty good hedge against inflation. Of course you have to be prepared for some odd looks when you use a calendar that appears to be half a decade out of date ;)