[whatwg] Issues relating to the syntax of dates and times

Tab Atkins Jr. jackalmage at gmail.com
Tue Nov 25 06:44:59 PST 2008

On Tue, Nov 25, 2008 at 7:36 AM, Pentasis <pentasis at lavabit.com> wrote:

> Ian Hickson wrote:
>  While I could see that maybe one day there'd be a use case for <time> that
>> would need historical dates, I really think that we'd have to tackle other
>> calendars in use today before looking at calendars that aren't in use
>> anymore. So I'd rather punt this for now.
> While it is true that there are to many factors to take into account
> regarding which calendar, which era, etc.
> I can also imagine, (just brainstorming here) if I look at this example in
> the spec:
> <p>We stopped talking at <time datetime="2006-09-24 05:00 -7">5am the next
> morning</time>.</p>
> This means I should also mark up something like this:
> <p>It was <time datetime="???">5 seconds after the big bang</time>.</p>

"5 seconds after the big bang" is an exceedingly ill-defined time, though.
Currently you'd be lucky to peg it within a billion years of the accurate
time, ignoring any relativistic issues with timekeeping.  This was Ian's
point about far-past dates being nearly never exact enough to justify a
machine-readable timestamp.

> There are more factors to take into consideration in this example than just
> calendars.
> So... Wouldn't it be far more efficient and convinient to have a
> construction by which we can set a "base-date/time"? (something like the
> base-url-thing). That way you can set the date/time to anything at all based
> on a reference-setting. And this reference setting could be anything
> (another calendar, a specific point in time (or perhaps even time-space) or
> a relative reference. I don't think this would have to be dealt with by the
> UA but can be done by scripting.

How does this solve the issue of the base time being too ill-defined for a
timestamp?  Assuming you have a basetime of "the big bang", you can
certainly exactly specify exactly 5 seconds after, but how would you specify
the basetime?

You're just moving the issue one level back.  This doesn't solve the
underlying issue that far-past dates aren't exact enough to give them a
timestamp.  This problem requires an entirely different solution, and trying
to shoehorn it into a timestamp-based solution just gives you two bad

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