A Wrinkle in Time

You've built a prototype, everything is going great. All your dates and times look great, they load and store correctly, everything is spiffy. You have your buddy give it a whirl, and it works great for them too. Then you have a friend in CuraƧao test it, and they complain that all the times are wrong - time zones strike again!

But, you've got this covered. You just add an offset to every stored date/time, so you know the origin time zone, and then you get the user's time zone, and voila! You can correct for time zones! Everything is going great, summer turns to fall, the leaves change, the clocks change, and it all falls apart again. Now you're storing dates in various time zones, without DST information, you're adjusting them to the user's time zone, trying to account for DST, trying to find a spot here or there where you forgot to account for offsets...

Don't fall into this trap. UTC is always the answer. It is effectively time-zone-less, as it has an offset of zero and does not observe daylight savings time. It's reliable, it's universal, it's always there when you need it, and you can always convert it to any time you need. Storing a date/time with time zone information is like telling someone your age by giving your birthday and today's date - you're dealing with additional data and additional processing with zero benefit.

When starting a project, you're going to be better off storing all dates as UTC from the get-go; it'll save you innumerable headaches later on. I think it is atrocious that .NET defaults to system-local time for dates; one of the few areas where I think Java has a clearly better design. .NET's date handling in general is a mess, but simply defaulting to local time when you call DateTime.Now encourages developers to exercise bad practices; the exact opposite of the stated goals of the platform, which is to make sure that the easy thing and the correct thing are, in fact, the same thing.

On a vaguely related note, I've found a (in my opinion) rather elegant solution for providing localized date/time data on a website, and it's all wrapped up in a tiny Gist for your use: https://gist.github.com/aprice/7846212

This simple jQuery script goes through elements with a data attribute providing a timestamp in UTC, and replaces the contents (which can be the formatted date in UTC, as a placeholder) with the date/time information in the user's local time zone and localized date/time format. You don't have to ask the user their time zone or date format.

Unfortunately it looks like most browsers don't take into account customized date/time formatting settings; for example, on my computer, I have the date format as yyyy-mm-dd, but Chrome still renders the standard US format of mm/dd/YYYY. However, I think this is a relatively small downside, especially considering that getting around this requires allowing users to customize the date format, complete with UI and storage mechanism for doing so.


On Code Comments

I've been seeing a lot of posts lately on code comments; it's a debate that's raged on for ages and will continue to do so, but for some reason it's been popping up in my feeds more than usual the last few days. What I find odd is that all of the posts generally take on the same basic format: "on the gradient of too many to too few comments, you should aim for this balance, in this way, don't use this type of comments, make your code self-documenting." The reasoning is fairly consistent as well: comments get stale, or don't add value, or may lead developers astray if they don't accurately represent the code.

And therein lies the rub: they shouldn't be representing the code at all. Code - clean, self-documenting code - represents itself. It doesn't need a plain-text representative to speak on its behalf unless it's poorly written in the first place.

It may sound like I'm simply suggesting aiming for the "fewer comments" end of the spectrum, but I'm not; there's still an entity that may occasionally need representation in plain text: the developer. Comments are an excellent way to describe intent, which just so happens to take a lot longer to go stale, and is often the missing piece of the puzzle when trying to grok some obscure or obtuse section of code. The code is the content; the comments are the author's footnotes, the director's commentary.

Well-written code doesn't need comments to say what it's doing - which is just as well since, as so many others have pointed out, those comments are highly likely to wind up out-of-sync with what the code is actually doing. However, sometimes - not always, maybe even not often, but sometimes - code needs comments to explain why it's doing whatever it's doing. Sure, you're incrementing Frobulator.Foo, and everybody is familiar with the Frobulator and everybody knows why Foo is important and anyone looking at the code can plainly see you're trying to increment it. But why are you incrementing it? Why are you incrementing it the way you're doing it in this case? What is the intent, separate from its execution? That's where comments can provide value.

As a side note (no pun intended), I hope we can all agree that doc comments are a separate beast entirely here. Doc comments provide meta data that can be used by source code analyzers, prediction/suggestion/auto-completion engines, API documentation generators, and the like; they provide value through some technical mechanism and are generally intended for reading somewhere else, not for reading them in the source code itself. Because of this I consider doc comments to be a completely separate entity, that just happen to be encoded in comment syntax.

My feelings on doc comments are mixed; generally speaking, I think they're an excellent tool and should be widely used to document any public API. However, there are few things in the world more frustrating that looking up the documentation for a method you don't understand, only to find that the doc comments are there but blank (probably generated or templated), or are there but so out of date that they're missing parameters or the types are wrong. This is the kind of thing that can have developers flipping desks at two in the morning when they're trying to get something done.