Archive for January, 2012

The best of <time>s

(Article updated to correct some typos noticed by commenters, and clarify some aspects.)

Avid HTML5 watchers will know that the <time> element was dropped from HTML, then re-instated, with more New! Improved! semantics.

As before, you can put anything you like between the opening and closing tags – that’s the human-readable bit. The machine-readable bit is contained within a datetime attribute. Dates are expressed YYYY-MM-DD.

Previously, you could only mark up precise dates. So, 13 November 1905 could be expressed in HTML <time datetime="1905-11-13"> but November 1905 couldn’t be. This is a problem for historians where sometimes the precise date isn’t known.

Now, “fuzzy dates” are possible:

  • <time datetime="1905"> means the year 1905
  • <time datetime="1905-11"> means November 1905
  • <time datetime="11-13"> means 13 November (any year)
  • <time datetime="1905-W21"> means week 21 of 1905

As before, times are expressed using the 24 hour clock. Now, you can separate the date and time with a space rather than a “T” (but you don’t have to). So both of these are valid:

  • <time datetime="1905-11-13T09:00">
  • <time datetime="1905-11-13 09:00">

You can localise times, as before. Appending “Z” to the timezone indicates UTC (a way of saying “GMT” without it being comprehensible to normal people). Otherwise, use an offset:

  • <time datetime="09:00Z"> is 9am, UTC.
  • <time datetime="09:00-05:00"> is 9am in the timezone 5 hours behind UTC.
  • <time datetime="09:00+05:45"> is 9am in Nepal, which is UTC + 5 hours and 45 minutes.


In New! Improved! HTML5 <time>, you can represent durations, with the prefix “P” for “period”.

The datetime attribute “D” for days, “H” for hours, “M” for minutes and “XQ” for seconds. Just kidding – that’s “S”.

You can separate them with spaces (but you don’t have to). So <time datetime="P4D"> is a duration of 4 days, as is <time datetime="P 4 D">.

Using a “T” after the “P” marker allows you to be more precise: <time datetime="PT23H 9M 2.343S"> is a duration of 23 hours, 9 minutes and 2.345 seconds.

Alternatively, you can use a duration time component.

Whichever you choose, it’s represented internally as a number of seconds. Because of this, you can’t specify a duration in terms of months, because a month isn’t a precise number of seconds; a month can last from 28 to 31 days. Similarly, a year isn’t a precise number of seconds; it’s 12 months and February sometimes has an extra day.

You still can’t represent dates before the Christian era, as years can’t be negative. Neither can you indicate date ranges. To mark up From “21/02/2012 to 25/02/2012”, use two separate <time> elements.


The pubdate attribute (a boolean that indicates that this particular date is the publication date of the parent <article> (or, if there is none, the whole document) is currently missing from the W3C version of the spec, but is still current in the WHATWG version. Its status is unclear to me (but I’m still using it).

Update 10 August 2012: in response to a query, I checked again and pubdate is gone from both the WHATWG and W3C specs.

Nesting ARIA roles

A couple of people have asked me recently if it’s possible to nest ARIA roles. The answer: yes.

Not all of them, of course. Think of HTML elements; you can nest <div>s inside <nav>s and <nav>s within <header>s, but you can’t put an <a> inside an <input> or put an <input> inside another <input> – they just wouldn’t make sense.

In ARIA, it’s perfectly fine to have role=article inside role=main (which is completely analogous to an HTML5 <article> inside a <div id=”main”>.

It’s also fine (as far as I know) to have roles like main inside a <table role=”presentation”>. Although the table is presentational only (it’s an old-fashioned layout table), it doesn’t mean that all the contents are presentational – one cell could contain the entire main content of a site and therefore quite legitimately have a role="main".

The rule of thumb I use is: if your nesting feels right, it probably is right.

Note also that the HTML5 validator also validates ARIA. Even if your content isn’t HTML5, it’s still worth running it through the validator.

Note, I’m not an ARIA expert. Please, if I’ve made a mistake, let me know!

Beware Tim Berners-Lee’s elite squad of standards-avenging attack ninjas

It’s been whispered about for some time, but only now can the truth be revealed. The Large Hadron Collider at CERN was built in order to produce enough Higgs Bosons to turn ordinary ninjas into an elite squad of standards-avenging attack ninjas under the sole command of Sir Tim Berners-Lee, previously from CERN (co-incidence? I think not!).

Unnamed sources tell me that, as the Mayans nearly predicted, 2012 will be the year when misusing vendor prefixes will no longer be tolerated and manufacturers bastardising CSS Media Queries to do UA-sniffing will not go unnoticed.

Don’t believe me? Here is an artist’s impression of an actual photo of Tim Berners-Lee summoning his standards-avenging attack ninjas.

Cartoon Ninja using a computer with W3C logo on lid. Japanese text.

Tremble, proprietary-lovin’ developers!

Reading List – Vendor prefixes, mobile, monoculture

The first reading list of 2012 is themed, rather than the usual miscellany. It’s about the Open Web and the dangers it faces.

I’ve nailed my colours to the mast – most lately in The Pastry Box:

The Web is about communication. It connects many people who previously were isolated such as those with disabilities or those in oppressive regimes. It’s a World-Wide Web, not a Wealthy Western Web. If your super-clever site only works with a mouse and monitor, on the latest $2000 super-spec laptop, with a fat broadband connection, you’re missing the point.

The ideal of universality is fundamental to the Web. Some bloke called Tim said

The principles of universality of access irrespective of hardware or software platform, network infrastructure, language, culture, geographical location, or physical or mental impairment are core values in Web design.

One of the most worrying trends we see at the moment is the erosion of this idea. In a survey, Peter-Paul Koch asked "Do you hope that WebKit will become the only rendering engine, and that the others will gradually disappear?". Shockingly, 32% have replied “yes” (at time of writing). You read that correctly! 32% actively wish for a monoculture. Because, y’know, cross-browser development is hard – so let’s go shopping! Who cares about the users? Who cares about the future? We’ve been here before with IE6- the darling of developers at the time – and look how well that went.

It’s pretty obvious that this is a case of a group of developers that believes that everyone should be just like them and should use the same devices and browsers. After all, despite all their genuflecting to Safari on their iPhones, it appears from December’s mobile statisitics (as written up by PPK) that

Opera once more overtakes Safari. It’s clear now that Android’s untrammeled growth has ended, and that the race for first position will continue to be between Opera and Safari.

(If you’d like to start testing your sites in the number one mobile browser, there are plenty of Opera testing tools available. Note: Opera is my employer, but this is my personal opinion.)

Stephanie Rieger writes in A plea for progressive enhancement

we have to start building sites using solid, future friendly principles such as progressive enhancement…not just when it’s handy or simple, but all the time.

and goes on to show a Barack Obama re-election site in which it was impossible to navigate in many devices, even some new high-spec devices. In a news report about this, the journalist quotes my three incredibly ground-breaking, never-before-heard rules:

  • Code to standards, not to browsers
  • use progressive enhancement
  • remember that you are not your user.

Yes, I know! Utterly new concepts.

However, we’re approaching a monoculture on mobile. This is not the work of an evil organisation, but it’s developer-constructed. Few people are stupid enough to use Olde-Skool browser sniffing and blocking, but we’re seeing lots of people breaking cross-browser compatibility by neglect rather than design.

One way this happens is developers using only one vendor’s CSS vendor prefix even when other vendors support the same properties. Of course, for experimental things only implemented by one rendering engine, that’s fine. That’s what vendor prefixes are for.

The trouble comes about when people do something like -webkit-transition for widely-supported properties, without the corresponding -o- for Opera, -ms- for Microsoft and -moz- for Mozilla.

Last week, Mozilla developer Boris Zbarsky wrote

People never aim to create content that’s cross-browser compatible per se, with a tiny minority of exceptions. People aim to create content that reaches users. What that means is that right now people are busy authoring webkit-only websites on the open web because they think that webkit is the only UA that will ever matter on mobile. And if you point out this assumption to these people, they will tell you right to your face that it’s a perfectly justified assumption. The problem is bad enough that both Trident and Gecko have seriously considered implementing support for some subset of -webkit CSS properties.[my emphasis]

Three years ago, David Baron (also of Mozilla) wrote Should implementors copy vendor prefixes from each other?, and in 2010 Microsoft announced that it would support -webkit- prefixes, but eventually decided against it.

Since then, we’ve had many more debates about the merits of vendor prefixes (see previous reading list), and even the co-chair of the CSS Working Group, Daniel Glazman, wrote

The rule should be this one: if the CSS parser encounters a prefixed property for another browser, honour that property as if it were prefixed for us UNLESS an unprefixed or prefixed for us valid declaration for that property was already set. That would drastically reduce the problems on the Web.

I believe vendor prefixes were a good idea, and remain so if used in a cross-browser, future-proof way. But because so many people only use the -webkit- one, I’m starting to wonder too if vendor prefixes should be considered harmful

New Year’s Resolutions


  • Brand-new presentations to be written in web technologies, eg with Vadim’s cross-browser Shower
  • Become a better scripter
  • After last year’s heroic lost cause of attempting to prevent people using the term “HTML5” for everything, this year I shall be putting my finger in the dyke of everyone shouting for joy when a vendor uses first-mover advantage or market dominance to attempt vendor lockin
  • Learn to love Git. This one may prove tricky.


  • Diet – lose 10 kilos. This is closely related to…
  • Get my next karate belt, and train at least once a week.
  • Read more classic literature (I have 200 unread books on my shelves)
  • Take a photo every day
  • Play rhythm guitar in a band
  • Learn to play the bass guitar part to The Beatles “Rain” as well as this bloke does.