(Wow, it’s great to be 24 again! 
)
I can see where math would be required if the question were something like, “What day of the week must the 1st occur on if the month has a Tuesday the 23rd?” But Friday the 13th is more notable and thus the image of the corresponding (and simple) calendar layout sticks in the mind (at least for me).
I rarely look at actual calendars anymore and certainly don’t have them memorized or generally have an image of them complete with days and dates. It’s just not the sort of thing my mind retains. I would have had to either do math or count on my fingers to get to the answer.
This is how I solve it, saving at least a dozen milliseconds by sticking to small integers. That there are no “-1” dates is irrelevant.
Yikes. I just put a calendar in my head (as though I’m picturing it) and look at the first of the month. I know a week is 7 days, so my numbers “fill out” easier…
…if that made sense.
Clearly not a math teacher.
Me, three. This is something I’ve known for years, as Friday the 13th is such a noteworthy date when it occurs in a month. You don’t have to remember every possible combination for days in a month. It’s just one of those things you learn by observing, like New Year’s Day coming exactly a week after Christmas.
Um, have I mentioned I’m bad at math?
I don’t know if it’s very mathematical, but what I did was “13friday minus 14 leaves me in the previous month, 14saturday minus 14 still no go, 15sunday minus 14 leaves 1sunday”.
FTR, nothing particular about friday the 13th where I come from, other than “it’s a day that’s considered ill-luck by some foreigners, thus the name of the gore movie series”.
I’d go the Fri13-Sat14-Sun15-Sun1 route. While I’ve never used negative dates like septimus and constanze did, I have used dates like “July 73rd”.
And not that this will ever be of use to anyone, but remember the phrase “I work 9 to 5 at the 7-11.” 9/5, 5/9, 7/11, and 11/7 in the same year are all the same day of the week. These days are the same as the last day in February (28th or 29th, aka “3/0”) and 4/4, 6/6, 8/8, 10/10, and 12/12. The only one that’s hard to remember is “1/3 three years, but 1/4 in the fourth year”, because then you need to know where leap years are.
I guess I go 1, 8, 15. So if the fifteenth is 2 days after the thirteenth, it must be a Sunday, and likewise the first.
Now in 1968, my friend got had by the the fifth Tuesday in February.
Pretty sure Rebecca Black covered this already…
That’s basically how I (and anyone) can quickly figure out what day of the week, say, this coming January 20th will fall on, i.e. today is Thursday December 22nd, so the 29th, 36th, 43rd, and 50th of December are also Thursdays. But the 50th of December is really the (50 - 31) = 19th of January. So, the 20th must be a Friday.
(all this sounds slower and more complicated than it actually is).
Does anyone else remember an Encyclopedia Brown story in which this was the way that he solved the mystery?
If friday is 13th, previous friday is 6th. Count backwards and sunday is 1st.
I noticed the relationship a couple of decades ago without math at all. I just looked at the months with Friday the 13th, and checked the day it started.
this is the easiest method to use under stress. just hold up your fingers and count backwards. you can’t go wrong.
“Friday the 13th fell on a Tuesday this month.”
I suppose it is a bit cultural. In my case during my formative years I did encounter a lot of people who thought Friday the 13th really was bad luck. From there it wasn’t much of a leap to notice that those “bad” days happen when the first is a Sunday. I can’t visualize any other calendar.
No, you aren’t. I’m guessing you also notice that September and December always start on the same day.
Meee!!! I’ve always remembered it that way.