Re: Using YY-MM-DD date input

Tom Lane wrote:
> Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > Does anyone use YY-MM-DD for date input?
> > We are considering eliminating it for 7.4.  You can still use
> > yyyy-mm-dd, or course.
>
> The way I think the date input parser should work when seeing three
> numeric values is:
>
> 1. If first field has four digits, then format is yyyy-mm-dd.

OK

> 2. If first field is larger than 31, assume format is yy-mm-dd.
>    (I'm not totally wedded to this, since it could be argued to be
>    allowing the input values to determine the interpretation, which
>    is exactly the kind of heuristic that people objected to in the
>    dd/mm vs mm/dd discussion last month.  It seems reasonable to me,
>    but it could be removed without affecting the rest of this proposal.)

I am not excited about this, though you could say it is an extension of
the 4-digit rule.  However, I don't like that 30-03-03 is in 2003 and
32-03-03 is in the year 32AD.  That seems error-prone to me.  :-)

> 3. Otherwise, the format must be one of yy-mm-dd, dd-mm-yy, or mm-dd-yy.
>    We should use DateStyle to decide which one of these applies.

I see this as a feature addition, because right now, in 2003, there is
no way to enter a current date with a leading year using only two digits.

Also, if there aren't many people who want it, I am concerned it will
cause confusion, because our datestyle stuff is already complicated.

> There are presently only two input DateStyles ('US' and 'European') but
> it would be trivial to add a third to accept yy-mm-dd.  We'd only need
> to figure out what to call it.  I'm tempted to just call it 'YMD' and
> provide 'DMY' and 'MDY' as alternative names for 'US' and 'European'.

Now, that is an interesting idea, and I wonder if they aren't better
than US and European (and German), because they are more general.

Is this something we want to do in feature freeze?

> We could also use datestyle to decide what to do with ambiguous inputs
> like 03-FEB-01 --- given a 3-way input DateStyle, I'd say YMD should
> mean that the year is first, while the other two mean the day is first.

Interesting.

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