Date shift on daylight saving in Brasilia UTC-3 with date.toString()

[stefanseeger]

Hello, on Oct 15, 2017 in Brasilia a daylight saving hour is applied.

GIVEN: the Maschine is set to UTC-3 Brasilian timezone

WHEN executing Javascript:
new Date ("Oct 15, 2017 12:00:00 AM").toString()

THEN: IE11 is falsely returning:
"Sat Oct 14 23:00:00 UTC-0300 2017"

EXPECTED is:
"Sun Oct 15 00:00:00 UTC-0300 2017" or
"Sun Oct 15 00:00:00 UTC-0200 2017" depending on who you ask ;)

Same problem applies to
new Date ("Oct 15, 2017 12:00:00 AM").toDateString() => "Sat Oct 14 2017"

Root cause seems to be that in Brasilia the daylight saving hour is at 12am.
Therefore, 12am - 1 hour is 11pm on the day before.
This probably can be applied to all time zones with the day light saving hour at 12am.

Please fix asap.
Thanks and best regards,
Stefan

[dilijev]

Not sure how this issue slipped under the radar for so long... sorry about that.

"Depending who you ask" is a bit vague, so I'd assume this is ultimately an issue with the globalization database. @jackhorton can you see whether ICU behaves differently from winglob (even though Date.p.toString is not an Intl API).

Repro'd on Windows by configuring with the following (note: you will need to reset your timezone later).

>tzutil /l
...
(UTC-03:00) Brasilia
E. South America Standard Time
...

>tzutil /s "E. South America Standard Time"

>tzutil /g
E. South America Standard Time

>tzset
America/Sao_Paulo

eshost repro shows lots of disagreement among the engines at the moment:

>eshost --tags jsvu -h ch-master-latest -ise "new Date ('Oct 15, 2017 12:00:00 AM').toString()"
## Source
print(new Date ('Oct 15, 2017 12:00:00 AM').toString())

#### jsvu-sm
Sun Oct 15 2017 00:00:00 GMT-0300 (E. South America Standard Time)

#### jsvu-d8
Sun Oct 15 2017 01:00:00 GMT-0200 (Brasilia Summer Time)

#### ch-master-latest, jsvu-ch
Sun Oct 15 2017 01:00:00 GMT-0200 (E. South America Daylight Time)

#### jsvu-jsc
Sat Oct 14 2017 23:00:00 GMT-0300 (E. South America Standard Time)

>eshost --tags jsvu -h ch-master-latest -ise "new Date ('2017-10-15T00:00-0300').toString()"
## Source
print(new Date ('2017-10-15T00:00-0300').toString())

#### ch-master-latest, jsvu-ch
Sun Oct 15 2017 01:00:00 GMT-0200 (E. South America Daylight Time)

#### jsvu-d8
Sun Oct 15 2017 01:00:00 GMT-0200 (Brasilia Summer Time)

#### jsvu-sm
Sun Oct 15 2017 00:00:00 GMT-0300 (E. South America Standard Time)

#### jsvu-jsc
Invalid Date

Note: we are not longer fixing non-security bugs in IE. If this is still an issue in Edge we will investigate.

[jackhorton]

/cc @jefgen, this looks like an NLS time zone issue

With that being said, how can expected be 00:00 UTC-3 or 00:00 UTC-2 depending on who we ask? Those are not the same time -- the options to me look like theyd be 23:00 UTC-3 or 00:00 UTC-2, which are the same absolute time. If the later is the case, then Chakra is printing out at least one of two expected values.

[dilijev]

(Updated my comment with a repro.)