6 ms·

I definitely thought the conclusion was going to be something like: "We need to loop over every day to count Thursdays, because of calendar shenanigans in Augus

I definitely thought the conclusion was going to be something like: "We need to loop over every day to count Thursdays, because of calendar shenanigans in August 1632 in Russia and February 1295 in the Holy Roman Empire, which caused there to be 0 and 21 Thursdays, respectively." Maybe I've read too many "Falsehoods Programmers Believe about X" articles. (The exceptions mentioned are made up. I don't know of any month that had a number of Thursdays other than 4 or 5.)

nerdponx 5y ago
I generally tend to (perhaps superstitiously) do things the "slow way" like this, for exactly this reason. This kind of thing is also generally why I don't understand people who don't like "dependencies" in general. If something requires specialized knowledge, I would much rather let the specialists work on it, than arrogantly assume I know enough to do it myself correctly.
- Jtsummers 5y ago
  There are (at least) two kinds of dependencies: 1. Complex libraries and mechanisms that you couldn't (or are complex enough that you wouldn't) make on your own. 2. leftpad. The former is worth using in many situations. I would not make any kind of network protocol implementation myself in most cases because, while I can, I don't have time to do it correctly (vice hiring a proper expert or purchasing/using an expert made implementation). The latter is the garbage that causes problems, for various reasons. The ubiquity, for instance, of this totally trivial package broke a lot of other systems when they could have been replaced with a very small (and easily shown correct) bit of your own code. The other problem is that they are opportunities for corruption of your system. The more dependencies you have (direct or indirect via transitive dependencies) the more attack surface area (poor code permitting an attack) or potential for others to insert attacking code (the code isn't just insecure, but it's actually the attack itself).
  - bobthepanda 5y ago
    The problem with dependencies is that you start relying on Other People's Support, and that can vary from package to package. The support you get from the Apache Foundation is going to be a lot different than the support you get from, say, a React community-maintained fork of an originally JQuery component that builds some oddly specific finicky frontend paradigm.
- recursive 5y ago
  > If something requires specialized knowledge This seems to be very much the point. I suspect there's actually disagreement about whether the thing actually requires specialized knowledge. If there were actually 700 days of February 1295 in the Holy Roman Empire, what are the chances that month would be handled correctly by any layer of my Thursday-counting Saas platform? A lot of times the "specialists" are just as likely to say something like "Dates before 1900 are not supported because they're too hard". And your app probably didn't care about those cases anyway.
salmonellaeater 5y ago
Samoa skipped a Friday in December 2011 [1]. There were 4 Fridays left so "4 or 5" still holds, but using arithmetic to calculate the number of Fridays would have yielded a wrong answer. This is pretty uncommon with whole days so maybe less important, but thinking in this way (how can I optimize this annoying code) often leads to wrong arithmetic around hours (daylight savings and time zone changes) or seconds (leap seconds). [1] https://www.abc.net.au/news/2011-12-30/samoa-skips-friday-in-time-zone-change/3753350 https://www.abc.net.au/news/2011-12-30/samoa-skips-friday-in...
madcaptenor 5y ago
In Britain and the (then-future) USA, September 1752 had three Thursdays - Wednesday, September 2 (Julian) was followed by Thursday, September 14 (Gregorian), and then there was Thursday the 21st and 28th. That month had only two Sundays and two Mondays. Other countries that made the Julian-Gregorian transition at other times will have similarly short months somewhere else in their history. There might be an instance of six of the same weekday in a month, if some area repeated the right day while moving from the Asian side of the international date line to the American side. Alaska's the only example I can find, but they also switched from Julian to Gregorian at the same time, so they had Friday, October 6, 1867 (Julian) followed by Friday, October 18, 1867 (Gregorian).

nerdponx 5y ago

I generally tend to (perhaps superstitiously) do things the "slow way" like this, for exactly this reason. This kind of thing is also generally why I don't understand people who don't like "dependencies" in general. If something requires specialized knowledge, I would much rather let the specialists work on it, than arrogantly assume I know enough to do it myself correctly.

Jtsummers 5y ago
There are (at least) two kinds of dependencies: 1. Complex libraries and mechanisms that you couldn't (or are complex enough that you wouldn't) make on your own. 2. leftpad. The former is worth using in many situations. I would not make any kind of network protocol implementation myself in most cases because, while I can, I don't have time to do it correctly (vice hiring a proper expert or purchasing/using an expert made implementation). The latter is the garbage that causes problems, for various reasons. The ubiquity, for instance, of this totally trivial package broke a lot of other systems when they could have been replaced with a very small (and easily shown correct) bit of your own code. The other problem is that they are opportunities for corruption of your system. The more dependencies you have (direct or indirect via transitive dependencies) the more attack surface area (poor code permitting an attack) or potential for others to insert attacking code (the code isn't just insecure, but it's actually the attack itself).
- bobthepanda 5y ago
  The problem with dependencies is that you start relying on Other People's Support, and that can vary from package to package. The support you get from the Apache Foundation is going to be a lot different than the support you get from, say, a React community-maintained fork of an originally JQuery component that builds some oddly specific finicky frontend paradigm.
recursive 5y ago
> If something requires specialized knowledge This seems to be very much the point. I suspect there's actually disagreement about whether the thing actually requires specialized knowledge. If there were actually 700 days of February 1295 in the Holy Roman Empire, what are the chances that month would be handled correctly by any layer of my Thursday-counting Saas platform? A lot of times the "specialists" are just as likely to say something like "Dates before 1900 are not supported because they're too hard". And your app probably didn't care about those cases anyway.

salmonellaeater 5y ago

Samoa skipped a Friday in December 2011 [1]. There were 4 Fridays left so "4 or 5" still holds, but using arithmetic to calculate the number of Fridays would have yielded a wrong answer. This is pretty uncommon with whole days so maybe less important, but thinking in this way (how can I optimize this annoying code) often leads to wrong arithmetic around hours (daylight savings and time zone changes) or seconds (leap seconds). [1] https://www.abc.net.au/news/2011-12-30/samoa-skips-friday-in-time-zone-change/3753350 https://www.abc.net.au/news/2011-12-30/samoa-skips-friday-in...

madcaptenor 5y ago

In Britain and the (then-future) USA, September 1752 had three Thursdays - Wednesday, September 2 (Julian) was followed by Thursday, September 14 (Gregorian), and then there was Thursday the 21st and 28th. That month had only two Sundays and two Mondays. Other countries that made the Julian-Gregorian transition at other times will have similarly short months somewhere else in their history. There might be an instance of six of the same weekday in a month, if some area repeated the right day while moving from the Asian side of the international date line to the American side. Alaska's the only example I can find, but they also switched from Julian to Gregorian at the same time, so they had Friday, October 6, 1867 (Julian) followed by Friday, October 18, 1867 (Gregorian).