Re: Error with the leap year

On Thu, Mar 01, 2012 at 08:26:13PM -0800, Michael G Schwern wrote:
> On 2012.3.1 2:14 PM, [email protected] wrote:
> > If the date for $dt is 20120229, the following produces an error!
> > 
> > $dt->set_year($dt1->year + 1);
> > 
> > Invalid day of month (day = 29 - month = 2)
> 
> This error is correct, there is no Feb 29, 2013.
> 
> It could return March 1, 2013... but then adding a year to Feb 29, 2012 and
> adding a year and a day give the same result which doesn't make sense.
> 
> It does present a problem... how do you reliably say "same date next year"?

This is very similar to the 'end_of_month_mode' feature in
DateTime::Duration, which handles how (for example) "Jan 30 + 1 month"
calculations are handled.  Therefore, I would suggest a configuration
option for handling how wrapping is done involving leap years.

For that matter, leap seconds pose the same problem - if 00:00:60 is a
leap second, how does one handle 00:00:60 + 1 minute? is it wrapped to the
next minute (00:02:00), truncated (00:01:59), or...?


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            .             .            .            .             .
Karen Etheridge, [email protected]       GCS C+++$ USL+++$ P+++$ w--- M++