created, issued, modified [Re: comments on Atom 0.2]

[Evan Martin <martine@xxxxxxxxx>]

On Fri, Aug 08, 2003 at 08:12:25AM -0700, Nelson Minar wrote:
> >If I post in PST but don't tag it with <issued>, then the only date the
> >blog tool has is the modified date, which is in UTC.  How would it know
> >the proper timezone to translate that date into when showing the date
> >you posted with?
> 
> I hadn't thought about that. So we'd like to know two different
> things: the absolute time that the entry was created, and the local
> time (to convey things like "this is a 3am rambling").
> 
> I still think <issued> should be optional; I don't think most blogs
> will usefully distinguish between the two, so it shouldn't be
> required. I also wonder if maybe best practice is not to make
> <modified> be *local time* with a timezone offset rather than UTC.
> That way you get both absolute time and the local time in one little
> timestamp.

That does make sense, but...

> That may pose a problem for sites like Blogger and LiveJournal,
> though, do they know what timezone their user is in?

No, we don't.  We treat the issued time as more or less a user-specified
attribute like the subject:  while it must be a time, that time is only
meaningful in the sense of "oh, they're posting at 3am (their time),
they must be up late".
(This isn't particularly intentional:  we'd like to support time zones
in the future, but we still have a lot of existing zoneless data...)

Thankfully, the spec Atom is using for times doesn't require a zone.

> Besides timezone, the other question in <issued> vs <modified> is
> whether issued is the creation time of the post and modified is the
> last modified time. Is that the intent? I could see that being useful
> in some cases, but still I think <issued> should be optional.

As I understand it:
 - created is the "real" create time;
 - modified is the "real" modified time;
 - issued is whatever time the person wants to say the post came from.
   (Consider Pepys' Diary.)

If that's right, then:
 1. created+modified are often not both needed, and that's allowed for.
    (The validator [and maybe the spec?] allow you to elide created.)
 2. If you wanted to post with a "real" issued time, it would seem that
    a single time, tagged with your local time zone, would represent all
    of your post's information.

Using both 1 and 2, then, the pseudocode that could be used by an
aggregator when displaying:
  unless (defined post.created) post.created = post.modified;
  unless (defined post.issued) post.issued = post.created;
That would reduce posts to one timestamp in the common case.

It seems reasonable to me on a five-minute analysis, but you'd
probably have to get some other people's input on it before it became
part of the spec.

-- 
Evan Martin
martine@xxxxxxxxx
http://neugierig.org