Weirdly, it works for year of 2007 and above.

2006 and above actually

More weird. It works correctly in IE/Edge, but Firefox exhibits the exact same bug.

clement.gutel@ - Thanks for filing the issue...!!

Could you please provide a sample test file to test the issue from TE-end.
This will help us in triaging the issue further.

Thanks...!!

Hi,

Not sure what you mean by TE, but the following code sample is enough to reproduce the issue.

for (let i = 0; i < 12; i++)
{ 
   console.log(new Intl.DateTimeFormat("en-US", {month: "long"}).format(new Date(2000, i, 1))); 
}

Thank you for providing more feedback. Adding requester "krajshree@chromium.org" to the cc list and removing "Needs-Feedback" label.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

clement.gutel@ - Thanks for your reply...!!

Unable to reproduce the issue on Win-10 and mac 10.12.6 using chrome reported version #62.0.3202.94, latest stable #63.0.3239.84 and latest canary #65.0.3292.0.

Attached a screen shot for reference.

Following are the steps followed to reproduce the issue.
------------
1. Opened dev tools console in chrome.
2. Pasted the code at comment #0 and observed that all months of the year displayed exactly once without any issues.

reporter@ - Could you please check the issue on latest stable #63.0.3239.84 by creating a new profile without any apps and extensions and please let us know if the issue still persist or not.

Thanks...!!

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Ok, I tried tweaking the time zone in my windows 7 machine, and this impacts this bug.

Following results occur in Incognito window

Canberra, Melbourne, Sydney => bug occurs
Pacific Time (US & Canada) => it's even worse. April is showing March, and November is showing October.
Central America => correct behaviour
UTC => correct behaviour

I'm pretty sure it's related to daylight savings. There must be a bug causing the daylight offset to be added to April 1st 00:00 causing it to move to March 31st 23:00, or something like that.

See this other bug I reported earlier this year, which was quite similar and was fixed.
https://bugs.chromium.org/p/chromium/issues/detail?id=722821
This may provide some good pointers.

See attached screenshot

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Thank you for providing more feedback. Adding requester "krajshree@chromium.org" to the cc list and removing "Needs-Feedback" label.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

Able to reproduce the issue on Win-10 using chrome reported version #62.0.3202.94 and latest canary #65.0.3293.0 as per comment #9.
Issue is not seen in OS-Mac and Linux.
This is a non-regression issue as it is observed from M50 old builds. 

Hence, marking it as untriaged to get more inputs from dev team.

Thanks...!!

Ah! Excellent!

This issue has been Available for over a year. If it's no longer important or seems unlikely to be fixed, please consider closing it out. If it is important, please re-triage the issue.

Sorry for the inconvenience if the bug really should have been left as Available.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot