63720 - setMinutes(), getTimezoneOffset() correct in GMT+ timezones?

Status: RESOLVED WORKSFORME

(Core :: JavaScript Engine, defect)

Description

[Phil Schwartau]

Note the behavior of setMinutes() and getTimezoneOffset() when I advance 
my WinNT system clock from Pacific Standard Time to London, then to Casablanca.
On WinNT, Casablanca and London both say they are GMT = 0, yet the return values 
of both the above methods differ between them. 

I am not yet able to decipher the ECMA requirement for the return value
of setMinutes(). If there is supposed to be something different between
the Casablanca and London timezones, OK - but then why does the Pacific
timezone give the same setMinutes() result as London does: 1020755220000?  
Whereas in Casablanca, setMinutes() gives 1020758820000 (one hour ahead)?


Notes; in the following, UTC_2000_JAN_01 = 946684800000. When we apply 
setMinutes(), we use a parameter of 1234567. This advances the date from 
UTC_2000_JAN_01 to a date of May 07, 2002. Of course, this means Daylight 
Savings Time will come into play...



PACIFIC STANDARD TIME (GMT -8)  *******************************************
new Date():
Mon Dec 25 13:00:30 GMT-0800 (Pacific Standard Time) 2000
new Date().getTimezoneOffset()/60
8

DateCase = new Date(UTC_2000_JAN_01)
Fri Dec 31 16:00:00 GMT-0800 (Pacific Standard Time) 1999
DateCase.setMinutes(1234567)
1020755220000
DateCase.getTime()
1020755220000
DateCase
Tue May 07 00:07:00 GMT-0700 (Pacific Daylight Time) 2002
DateCase.getTimezoneOffset()/60
7
DateCase.getUTCHours()
7



LONDON (GMT 0)  *******************************************
new Date():
Mon Dec 25 21:01:17 GMT+0000 (GMT Standard Time) 2000
new Date().getTimezoneOffset()/60
0

DateCase = new Date(UTC_2000_JAN_01)
Sat Jan 01 00:00:00 GMT+0000 (GMT Standard Time) 2000
DateCase.setMinutes(1234567)
1020755220000
DateCase.getTime()
1020755220000
DateCase
Tue May 07 08:07:00 GMT+0100 (GMT Daylight Time) 2002
DateCase.getTimezoneOffset()/60
-1
DateCase.getUTCHours()
7



CASABLANCA (GMT 0) *******************************************
new Date():
Mon Dec 25 21:02:14 GMT+0000 (Greenwich Standard Time) 2000
new Date().getTimezoneOffset()/60
0

DateCase = new Date(UTC_2000_JAN_01)
Sat Jan 01 00:00:00 GMT+0000 (Greenwich Standard Time) 2000
DateCase.setMinutes(1234567)
1020758820000
DateCase.getTime()
1020758820000
DateCase
Tue May 07 08:07:00 GMT+0000 (Greenwich Standard Time) 2002
DateCase.getTimezoneOffset()/60
0
DateCase.getUTCHours()
8

Comment 1

[Phil Schwartau]

Reassigning Mike's JS Engine bugs to Patrick, as per recent meeting - 

Comment 2

[Patrick C. Beard]

Marking future.

Comment 3

[Brendan Eich [:brendan]]

Possibly dup'd by bug 173431 ?  From [e-mail]'s post at
news://news.mozilla.org:119/ci6tfq$[e-mail], it seems that rogue
TZ setting can mess up Windows localtime.

/be

Comment 4

[Bob Clary [:bc] (inactive)]

-> default qa

Comment 5

[André Bargull [:anba]]

No longer reproducible, because Morocco observes daylight savings since 2008 and we don't track historical time zones.

>> DateCase = new Date(UTC_2000_JAN_01)
Date 2000-01-01T00:00:00.000Z
>> DateCase.toString()
"Sat Jan 01 2000 00:00:00 GMT+0000 (Morocco Daylight Time)"
>> DateCase.setMinutes(1234567)
1020755220000
>> DateCase.getTime()
1020755220000
>> DateCase.toString()
"Tue May 07 2002 08:07:00 GMT+0100 (Morocco Standard Time)"
>> DateCase.getTimezoneOffset()/60
-1
>> DateCase.getUTCHours()
7