Date.prototype.toISOString and Invalid Date

Christian Plesner Hansen christian.plesner.hansen at
Wed Jun 10 01:50:47 PDT 2009

If the spec says that toISOString() must return a certain value that
doesn't parse according to maybe, for symmetry, it should
also say what Date.parse should do when passed that value?

On Wed, Jun 10, 2009 at 3:06 AM, Allen
Wirfs-Brock<Allen.Wirfs-Brock at> wrote:
> Currently, implementations are inconsistent about what they produce for (new Date(NaN).toString()).
> IE and Opera produce "NaN", while FF and Safari produce "Invalid Date".
> Since toISOString is a new function, we have the opportunity to specify what we want the result to be.
> Does anybody have an opinion. It could be either "NaN" or "Invalid Date" or something else. "Invalid Date" has the advantage that it is more end-user meaningful if it actually leaks through to be visible on a web page (although that is a pretty Anglo-centric perspective).
> Unless, I here strong opinions otherwise I think I'll go with "Invalid Date".
> Allen
>>-----Original Message-----
>>From: es-discuss-bounces at [mailto:es-discuss-
>>bounces at] On Behalf Of Garrett Smith
>>Sent: Saturday, June 06, 2009 12:40 AM
>>To: es-discuss
>>Subject: Date.prototype.toISOString and Invalid Date
>>What is the expected result of calling toISOString on a date where the
>>year is NaN?
>>var d = new Date(NaN);
>>es-discuss mailing list
>>es-discuss at
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