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Comment by sshine | Hacker News Reader

I count difference between small numbers and enums on my fingers.

This includes e.g.

  - the distance between months
  - the distance between wall clocks

It's simpler for me to say "The number of months between March and September is... April, May, June, July, August, September, six." than "The number of months between March, 3, and September, 9, is 9-3 = 6," because I don't cache the numeric value of the months. Maybe I would if I were a Chinese speaker, where September's name is 九月 jiǔ yuè = nine month.

For wall clocks that wrap around midnight, it's simpler to count because it removes dealing with negative numbers.

I count the number of days in a month on my knuckles.

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I check my knuckles if its 30/31 days in a given month. Start counting months on first knuckle while including the depth between knuckles as well. Height means 31, depth means 30.

I still do this as well. I never understood why the little poem was so popular. At that point it’s just coming down to rote memorization, as pretty much any month can be used in any order and it will still sound right.

The thing one does need to remember with the knuckle method is to count the end twice before going back the other way. July and August are both 31. I suppose this isn’t an issue if 2 fists are used, but I was taught to use one, so I could use my finger to track and feel the peaks and valleys.

What's wrong with the poem?

  Thirteen days have November
  April, May, and December.
  All the rest have thirty nine
  except for February when the weather is fine.

Works for me.

Never realized I could use my finger tips for doing the same.

I do this as well. It's very handy (no pun intended).

September is a funny choice to use as an example, because it is named after a number (sept-: prefix, 7). The wrong number, though.

So remembering this little tid bit would do more harm than good

All of the months with numerical prefixes are wrong by the same offset, though. So as long as you remember that as well, it can be useful. Particularly since they're the last ones and thus take the longest to count to.

This is because September used to be the seventh month. March was the new year and coinsided with spring planting, the spring equinox. At some point we switched from a solar calendar to a lunar one and that's when the new year month changed. Source for all this is the dead sea scrolls, see the book "Ancient Mysteries of the Essenes" for a deep dive on our calendar.

Sept, Oct, Nov, Dec. My favourite months, wish they still where 7-10.

I thought the reason is because they added two months named July and August after emperors, which offset all the numbers by 2. (Sept, Oct, Nov, Dec - 7, 8, 9, 10)

That happened later, well after January and February had been added. I think the twelve month Roman calendar was from pre-history so we don't know when or why it was done. July and August were Quintilis and Sextilis, five and six.

Yeah, seems like I mixed my calendar history up. Reading this set me straight: https://en.m.wikipedia.org/wiki/Roman_calendar

Thanks for the reply, it led me to look into it deeper.

so, for those who haven't heard it yet...

why do programmers get Halloween and Christmas confused?

because oct(31) == dec(25)

Same with Quartember, Quintober, Sextober, October, November, and December.

Although in general I also count the difference in months on my fingers, this particular example from March to September just automatically pops a "six" because they are both ends of financial quarters. "Three months after Feb?" I need to count. "Three months after March? That's the next quarter, so June."

/!\ Months are intervals and suffer from the off-by-one problem.

If you count from the 15th to the 15th, fine.

But if you start on March 1st, finishing in September means 7 months, not 9-3=6. That’s when my fingers help me visualize full months.

Yeah, I think that might well be why I stick to finger counting, so I don’t accidentally count the offset as the first step.

The months after July are named after numbers, but the names are from the old calendar when the year started in March.

The months after August are named after numbers.

July and August form the Caesarian section.

Ah, so October is the official month of births as it comes after this "c section". Pun intended.

As a fun reminder of how different people are, the months to me are basically only their numeric value, and if someone starts taking about October I think to myself "October? Oh ya, the 10th month, got it."

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