923639 - Date.prototype.toLocaleFormat() returns unexpected values for years < 1900

Status: RESOLVED DUPLICATE of bug 818634

(Core :: JavaScript Engine, defect)

Description

[Christopher Williams]

User Agent: Mozilla/5.0 (X11; Linux i686; rv:24.0) Gecko/20100101 Firefox/24.0 (Beta/Release)
Build ID: 20130910160258

Steps to reproduce:

(new Date(1898, 0, 2, 12, 0, 0, 0)).toLocaleFormat("%C")
(new Date(-1, 0, 2, 12, 0, 0, 0)).toLocaleFormat("%y")
(new Date(-1, 0, 2, 12, 0, 0, 0)).toLocaleFormat("%Y")

User agent string, for reference, is:
"Mozilla/5.0 (X11; Linux i686; rv:24.0) Gecko/20100101 Firefox/24.0"


Actual results:

"99"
"99"
"-1"


Expected results:

"18" ( == Math.floor(1898 / 100) )
"01"
"-0001" (%Y should be four digits if I'm interpreting the strftime documentation correctly)

Comment 1

[Loic]

Manye bugs have been filed about "date" issues, like bug 868496, bug 911649.

Comment 2

[石庭豐 (Seak, Teng-Fong)]

I can confirm the *results*, but I cannot confirm the bug because the "expected results" are arguable.  I would split this bug to three child bugs if I were you, one for each format.

For %C, yes, it is indeed a bug for year between 1 and 1899. By the way, it's totally broken for Windows platform.  For year 0, it's arguable in definition whether it exists or not -- AFAIK, in ISO8601, year 0 = 1 BC, so it's quite confusing. For years less than 0, maybe they are simply undefined as far as JavaScript is concerned at current stage? CF notes below

For %y, for year bigger than 0, the result is correct. So the summary is not correct for this case. Problem arises when year is less than 0 and we're back to the same discussion above for %C.

For %Y, it's never written that %Y should be four digits.  From http://pubs.opengroup.org/onlinepubs/007908799/xsh/strftime.html :
%Y  is replaced by the year with century as a decimal number. 
(new Date(993, 0, 2, 12, 0, 0, 0)).toLocaleFormat("%Y") gives 993 seems alright to me.
But for
(new Date(-1, 0, 2, 12, 0, 0, 0)).toLocaleFormat("%Y") which gives -1
it's hard to say.  Either it should be undefined, or it should be -1XX because century zero does not exist.
________

After a rough reading, I can only find the following extracts relevant to our problem here. 

Note#1: (Extracted ECMAScript Edition 5)
To represent years before 0 or after 9999, ISO 8601 permits the expansion of the year representation, but only by prior agreement between the sender and the receiver.

Note#2:(Extracted from ISO 8601:2004)
Calendar years are numbered in ascending order according to the Gregorian calendar by values in the range [0000] to [9999]. Values in the range [0000] through [1582] shall only be used by mutual agreement of the partners in information interchange.

Comment 3

[André Bargull [:anba]]

toLocaleFormat was removed in bug 818634.