Date.prototype.toISOString and Invalid Date

Allen Wirfs-Brock Allen.Wirfs-Brock at
Tue Jun 9 18:06:46 PDT 2009

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".


>-----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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