When ever i see "never implement your own...", i know i want to implement it myself. People say that about hard things, and I only want to do hard things. Nobody wants people who can do easy things, people want people who can do hard things. The only way to learn how to do hard things, is to do hard things, so do the hardest things.

So go ahead, write your own date library, your own Unicode font rendering, compiler, OS, game engine or what ever else people tell you to never do because its hard.

Some things are good hard, the kind of hard that's driven by an interesting domain, going deep with well-architected tools or systems, learning lots of cool stuff.

I expect datetime-adjacent code is basically the opposite of all of this. All the hard parts are driven by fiddly adherence to real-world geography, politics, physics/astronomy, etc. There's no underlying consistency from which a sane model can be extracted, it's just special cases and arbitrary parameters all the way down.

I'm up for a challenge of course, but all else being equal, I'm happy to leave work that is the "bad hard" to others.

By all means, write it. Just don't use it. These warnings are almost always in the context of code you're going to release, not exercises in learning on your own.

I get wanting to do hard things, but do you write in binary? Do you crank your own electricity?

My most valuable resource is time. Sure, I could learn more low-level aspects of my craft ... and sometimes I find it useful to do so.

When I focus on doing the hardest, already solved things by re-implementing them my own way, what value am I adding?

I've never met a client who cared about a library or how I did something in code - until it broke. Then, they didn't care who wrote it, they just cared it started working again.

> The only way to learn how to do hard things, is to do hard things, so do the hardest things.

and i don't want to pay my employees to learn, i want to pay them to produce output i can sell.

Doing hard things are good, if this hard thing has never been done before - like going to the moon.

Doing hard things which has been done, but just not by you, is not good unless it's for "entertainment" and personal development purposes - which is fine and i encourage people to do it, on their own dime. Like climbing Mount Everest, or going to the south pole.

But if you are doing a project for someone else, you don't get to piggy back your personal wants and desires unrelated to the project on to it.

I can't believe this is such a controversial take. Solving hard things by yourself is growth. I 100% agree, rather solve a hard solved problem yourself than learning yet another JS framework or launching yet another revenue losing SaaS ("successful" because of VC). Or whatever. Push hard boundaries.

> People say that about hard things, and I only want to do hard things.

That's perfectly fine. Your time, your hobbies.

> Nobody wants people who can do easy things, people want people who can do hard things.

No, not really. People want people who do easy things, because they are clever enough to avoid needlessly wasting their time having to do hard things when they could have easily avoided it.

It's your blend of foolish mindset that brought us so many accidental complexity and overdue projects. There's a saying: working smart instead of working hard.

> So go ahead, write your own date library, your own Unicode font rendering, compiler, OS, game engine or what ever else people tell you to never do because its hard.

You can cut it out, this isn't LinkedIn.

> When ever i see "never implement your own...", i know i want to implement it myself.

Doing stuff for learning is useful, and the intent behind this general phrase is to not ‘implement your own’ something which is both hard and critical in a production environment. I work in cryptography (for security purposes) and have implemented quite a few things myself to learn, but I still use stable, field tested, and scrutinized crypto for any actual use.

> People say that about hard things, and I only want to do hard things. Nobody wants people who can do easy things, people want people who can do hard things.

Only wanting to do hard things limits yourself quite a bit: what about things which seem easy but could be improved? I worked in a non-tech related medical manufacturing job for a bit and took time to learn the process and tools. Afterward, I implemented a few tools (using what my coworkers (who have no programming or IT experience) have available to them: Excel and the VBA on the lab computers) to help them prep inventory lists which they have been doing by hand. Doing it by hand took them 3 hours as a group (and the first shift had to do this every morning), which my tool did in 5 seconds with a single button click. They still use it to this day, about a decade later.

This wasn’t something ‘hard:’ I glued a few files together, grouped a list by a filter, sorted the groups by a column, and made a printout which was easy to read and mark on as they went about their day. However, my coworkers didn’t even know this was possible until someone came in with a different skill set, learned what they did (by doing the job well for months) and then made a solution.

You must be careful with doing only ‘hard’ things. It requires other people to identify what is hard! In addition: crackpots do only hard things and believe they find better solutions than what exists so far (without consulting or learning about what has been done). Interesting people learn about things as they are (with the humility of knowing that they are not experts in most things) and tries to improve them using the knowledge they already have.

Don’t waste your time rolling your own crypto when you could do the _actual_ hard thing and identify unaddressed space to make careful and considered improvements.

It's not because it's "hard".

It's all about the nuisance created by human behavior. Calendar, DST, timezone, all the problems you never imagined can happen and can only be met in real life scenarios, and you will meet same problem again, struggle then found out the same problem have been solved long time ago by mature library, and the solution doesn't require any smart or advanced technique, just another corner case.

I think in the case of the article the date library isn't necessarily hard but tedious. They mention most date libraries suffer from supporting too many standards or allow ambiguity.

I agree with you though, do the hard things even if it doesn't work 100% right you will have learned a lot. In university I had to implement all of the standard template library data structures and their features, it wasn't as robust as the actual STL but the knowledge of how those work under the covers still comes up in my day to day job.

There are different kind of hardship though.

There things which was a result will make your mind click to an other way to comprehend a problem space and how to navigate through it.

And there are things which are hard due to pure accumulation of concurrent conventions, because of reasons like coordinating the whole humanity toward harmony with full happy peaceful agreement of everyone is tricky.

Handling date is rather the latter. If you dig in the lucky direction, you might also fall into cosmological consideration which is a rabbit hole of its own, but basically that's it: calendars are a mess.

I find this a perplexing comment in view of the fact that almost all of the linked article is in fact about how the author wrote his own date parsing library; the "never do it" bit is just a couple of lines at the start and so far as I can tell is mostly there for fun.

(In particular, at no point does the article actually argue for not writing your own date parsing library. It just says, in essence, "Never do it. I did it. Here's what I did and why.")

> Nobody wants people who can do easy things, people want people who can do hard things.

No, people want people that can provide value regardless of the difficulty. What you're describing is how we end up with not invented here syndrome.

Missing context is - there is always something else you work on like the guy was making Eleventy so it was waste of his time.

If you work for a company and build todo app most likely it will not be beneficial for you to implement in-house library because there will be stuff that will bring much more value.

Like you don't have now 2 years to cover for all hard stuff because you have to make synchronization of tasks between devices and your boss most likely won't appreciate that.

"Never roll your own cryptography" is always used in context of building another application it is never "don't become a cryptography specialist".

> So go ahead, write your own date library, your own Unicode font rendering, compiler, OS, game engine or what ever else people tell you to never do because its hard.

You can absolutely do these things. What you need to be aware of is that in most cases maintaining these things to a production quality level is full-time job for a talented engineer. So you shouldn't attempt these IF:

- You have a higher-level aim you are also trying to achieve

- You need a production quality implementation

If one of those isn't the case then knock yourself out.

Don't forget to roll your own crypto libraries.

It's so tempting to tell you "never implement your own html parser using regular expressions" just to make you do it.

I triple dog dare you!

https://www.youtube.com/watch?v=mc6pk2FRhbA

In a scenario where a programmer has to do this for work and might naively think that date handling is simple, the title is invaluable advice. It is one of those things that can cause real trouble.

OTOH writing, e.g., your own renderer could cause some funny display at worst and maybe some unnecessary effort.

This past 22nd of July was the shortest recorded day [0]. How would your library handle this?

[0] https://www.space.com/astronomy/earth/earth-will-spin-faster...

Writing an OS. I've learned more about computers, hardware, CPU design, compilers, etc. that have translated into literally every other facet of my IT world than I could have done without this project.

Definitely agree.

Yes. Do it.

The only way you understand X is by making your own X and trying to support it for a few decades, and our industry needs more people who understand X; fewer who just ask chatgpt/stackoverflow/google for "the answer".

Software companies make money by providing value to their customers via the software they provide. How does reimplementing a hard but already well-solved problem align with their goals? How does that compare with solving a hard problem for which there are no good solutions yet?

There's hard and then there's "there are so many unexpected edge cases you'll surely be cut if you touch that code," which not fun-hard.

This is the latter.

I feel obligated to comment on this.

Due to my work I rely on web scraped data for cybersecurity incidents. For Amazon Linux, they are disclosed with the fvcked up US datetime format (Pacific Time) and not in ISO8601 formatted strings which could imply Juliet/Local time.

In 2007 there was a new law that changed when Pacific Time enters/leaves Daylight Saving Time. Instead of making this fixed by a specific Day of a specific Month in numbered form like say "YYYY-03-01 to YYYY-10-01", they literally wrote the law quoting "first Sunday of April" to "last Sunday in October". Before 2007 it was "Second Sunday in March" to "first Sunday in November".

I'm not making this shit up, go ahead and read the law, come back and realize it's even more complex for other timezones, because some nations seem to make fun of this by going to +14:00 hours and -11:30 hours depending on the president's mood on Christmas or something.

In order to find out the Day of a specific calendar date, there's this cool article about Determination of the day of the week [1] which is quite insane on its own already. There is no failsafe algorithm to do that, each method of determining the day of the week has its own tradeoffs (and computational complexity that is implied).

Then you need to get all Sundays of a month, count the right one depending on the year, map back the date to ISO8601 and then you know whether or not this was daylight saving time they're talking about. Also make sure you use the correct local time to shift the time, because that changed too in the law (from 02:00LST to 03:00LDT and 02:00 LDT to 01:00LST before, to 02:00LST to 03:00LDT and 02:00LDT to 01:00LST after the changes).

Took me over 4 fvcking weeks to implement this in Go (due to lack of parsers), and I hate Amazon for this to this date.

PS: Write your own Datetime parser, this will help you realize how psychotic the human species is when it comes to "standards". After all this I'm in huge favor of the Moon Phase based International Fixed Calendar [2]

[1] https://en.wikipedia.org/wiki/Determination_of_the_day_of_th...

[2] https://en.wikipedia.org/wiki/International_Fixed_Calendar

Corporations and government certainly want people who can execute things that are easy, but reliably and consistently

Yea, date time parsing is probably fine so is rolling your own auth, unicode, font rendering, compilers.

Datetime libs themselves? No thanks.

Yeah but never ever roll your own encryption, or do it but never trust it.

Never write your own multi-planetary date/time library in brainfuck.

… but if you plan to sell it, don’t build your own billing system!

you want to do something people really think is hard? use C. it's not safe.

all the people who say C is not safe have downvoted me for quoting them

Solve new hard things instead of solved hard things.