[whatwg] Historic dates in HTML5

jim at eatyourgreens.org.uk jim at eatyourgreens.org.uk
Thu Mar 5 06:04:26 PST 2009

On Thu, Mar 5, 2009 at 12:56 PM, James Graham <jgraham at opera.com> wrote:
> Philip Taylor wrote:
>> and make sure their stylesheets use the selector ".time" instead of
>> "time", to guarantee everything is going to work correctly even with
>> unexpected input values.
>> So the restriction adds complexity (and bugs) to code that wants to be
>> good and careful and generate valid markup.
> On the other hand the python datetime class doesn't seem to support years
> 0 at all so consuming software written in python would have to
> the whole datetime module, potentially causing incompatibilities with
> party libraries that expect datetimes to have year >= 0. This seems like a
> great deal more effort than simply checking that dates are in the allowed
> range before serializing or consuming them in languages that do support
> years <= 0.

I think limiting the HTML5 spec based on the capabilities of user-agents
(or client software) is dangerous. Firstly, software capabilities change
over time as features are added/removed. Secondly, capabilities vary
between languages and applications. To add to Philip's examples, mysql
datetimes are restricted to years >= 1000 while MS Sql Server will not
accept datetimes prior to 1752. Hence developers parse dates into their
components and use integer types, not datetimes, for very old stuff. Should
HTML5 cater to the lowest common denominator and refuse datetimes before

Henri is right that the spec should be driven by the needs of authors to
markup specific information online and the value of adding particular
semantics to the web. If I'm the only publisher who sees a value in marking
up historical dates then that's nice, but I'll accept that the HTML spec
shouldn't change to accomodate my individual needs.

However, Henri is also right that a limited datetime in HTML needs to be
absolutely clear in the spec too, which it isn't at the moment.


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