Some news articles have reported the 1986 calendar is accurate for 2014. Aren’t there more recent years that match for 2014?
How many calendars would you need to own before you could stop buying and just recycle?
Whats the formula or relationship? Is it linear? Would the 87 calendar work in 2015? 88 in 2016?
Not sure about the formula, but I believe there would be 14 calendars - seven each with January 1st starting on Sunday - Sat and seven more with a day added for February 29.
As far as making the days line up right, you only need 14 calendars… 7 each having Jan 1st on a different day of the week, plus another 7 for the same situation but used in leap years.
But they don’t cycle through those 14 in simple progression. 14 isn’t easily divisible by 4 (for the leap year), so it jumps around.
WAG, since 28 years is a multiple of 14 and 4, I would guess if you had 28 calendars, you could set them up in a continual cycle, until you hit a “leap year exception” year like 2100.
Since 1986 is 28 years ago, I assume this is why they are saying that. 14 years after 1986 was 2000, which if I remember was an “exception to the leap year exception” year.
See this site:
It looks like you could use your 2003 or 1997 calendar this year.
Wall calendars with nice photos were $12 and up just before Christmas. Reusing them would make sense. After 11 years in a box the pictures would be new again. 
A buck a month just to have a Wall calendar is excessive. I miss the free ones drug stores used to give out.
I recycle my calendars, and all I need are 7, one starting on each day of the week. When there’s a leap day I just start using the next calendar.
Notice the cycle pattern of years: 6, 11, 11, … . Which adds up to 28 or 4 times 7. Not being a leap year it repeats more often. Other non-leap years have the same pattern. While leap year cycles are every 28 years.
But … the century years throw things off since they are usually not a leap year. 2000 was an rarity.
But what do you do on Feb 29 of a leap year? None of those calendars will tell you what the correct date is, so you’ll be left guessing all day long. 
That’s a smart idea for dealing with leap years. Seven calendars would be very easy to tuck away in a drawer for reuse.
I’d think you would need to avoid keeping a leap year calendar? That would start correctly Jan 1 but would be a day off after Feb 29.
But what about all the appointments and such written on them? I’d have to scratch all that out. I get many free calendars from VFW etc. We usually have 7 or 8 to give away.
You’re lucky. It’s been years since I got a free Wall calendar. I loved the Rexall calendars with the Farmers Almanac quotes. Great reading.
I get a free calendar from my Insurance agent. A tear off kind with a wing that props it up on my desk. They always fall over if the desk gets bumped.
Free wall calendars? Fatwallet is your friend.
Maybe it’ll be a nice diversion from the DM.
I take the day off, and don’t have to know what day it is.
Except for the stuff you want to keep.
My grandmother used to have a calendar in her sewing room wall, with days marked for the birthday and age for each of her many children and grandchildren. so she could remember to send each one a birthday card (with a crisp $1 bill and a personal message enclosed). She got a new calendar each year at the Christmas Eve Midnight service, and spent an hour or so each day until New Years copying over the dates from the old calendar onto the new one, and adding one to each age.
As stated, 14 calendars will always suffice. And ignoring ordinary century years (that is, not divisible by 400) calendars will recycle every 28 years. If you are crossing an ordinary century year, I think I once calculated that it actually recycles after only 12 years. And the calendar as a whole recycles without exception every 400 years. You might think it ought to require 2800 years but the number of days in 400 years just happens to be divisible by 7. Aside from 400*52 weeks, there are 497 extra days (including 97 leap days) and that number is obviously divisible by 7. So if 2000 began on a Sunday (as I think I recall), then 2400 will also begin on a Sunday. On the other hand, if you want a recent calendar that duplicates 2014, just go back either 5 or 6 depending on how many leap years have intervened. Let’s see, 2014 - 5 = 2009. Nope, only one leap year. 2014 - 6 = 2008. No, that’s a leap year. In that case, go back 11 years to 2003. That should work. Yes, three intervening leap years.
I keep all my calendars, and once hung up an old one that was the same as the current year. The office tightass actually complained that I didn’t have the “right” calendar on my wall.
Usually I’m the guy that people are talking about in the “People still use X?” commentary, but finally I get to dish it out!
People still use paper calendars? That was about the first electronic thing I switched to using almost exclusively.
Just for another slant on the OP’s question about a “formula” there’s this little thing my dad told me as a kid:
The quickest that the same day of the month can return to the same day of the week is either 5, 6, or their sum 11, or if it’s Feb/29 then 28, years.
Not a lot of help, but still useful details.
Maybe reading Perpetual calendar - Wikipedia could help.
I have been unable to locate a picture of the device I described in this post from Why does February only have 28 days? which is a fun thread that went up just shortly after I arrived at SDMB.