Bug 4892 – Date constructor has problems with months larger than 11

• Component: JavaScriptCore
• Status: RESOLVED FIXED

[Ruairi Mc Comb]

When creating dates in the following manner:

new Date(year, month, date);

If the month is larger than 11, the date returned starts going random. 

I've tested the page with Firefox (1.0.6 OSX, 1.0.1 & 1.0.6 WinXP) and IE (WinXP 6.0.2900) and if the 
month is larger than 11 these browsers update the date accordingly (e.g. if month is 13, they add 1 
year and 2 months).

[Ruairi Mc Comb]

Created attachment 3820 [details]
Demonstration of the bug.

[Mark Rowe (bdash)]

Confirmed with WebKit 412.7 and ToT WebKit.  In the ECMA 262 spec, section 15.9.1.12 (the MakeDay 
operator) it mentions that the year should be set to year + floor(month / 12), and the month to month % 
12.  This logic is currently implemented in date_object.cpp's fillStructuresUsingDateArgs.  The Date 
constructor does not make use of this function, so the adjustment never takes place.  It looks that 
Date.UTC suffers from the same problem.

[Mark Rowe (bdash)]

Created attachment 3858 [details]
Patch to wrap month around inside Date constructor, and Date.UTC.

I will add some layout tests shortly.

[Mark Rowe (bdash)]

Created attachment 3866 [details]
Layout test

This layout test covers both the Date constructor and Date.UTC.

[Darin Adler]

Comment on attachment 3858 [details]
Patch to wrap month around inside Date constructor, and Date.UTC.

This fix doesn't look right to me. I think handling things like this is part of
the job of the makeTime function, so we should fix that instead of doing this.

[Mark Rowe (bdash)]

Created attachment 3868 [details]
Updated patch

This patch moves the existing month wrapping from inside
fillStructuresUsingDateArgs into makeTime so that it handles the Date
constructor and Date.UTC case.

[Darin Adler]

Comment on attachment 3868 [details]
Updated patch

Looks great. One complaint: The comment mentions CFGregorianDate overflow, but
that's only one reason to adjust the year and do %= on the month. The other is
to work best with the year offset machinery, and it applies even on
non-Mac-OS-X.

[Geoffrey Garen]

*** Bug 4782 has been marked as a duplicate of this bug. ***

[Kevin Smith]

Has this actually been released in the latest version of Safari 2.0.4?  Because I still have a problem with this code:

var test = new Date(this.VisibleDate.getFullYear(),this.VisibleDate.getMonth()+(this.MonthRows*this.MonthColumns);

[Darin Adler]

(In reply to comment #9)
> Has this actually been released in the latest version of Safari 2.0.4?

No. It's fixed for Safari 3.