Date filter converts time to local timezone

Hi there,

There is an issue with the date filter that uses javascript’s native dates. The timezone of the javascript date is always set to the user’s timezone (this is different behaviour than in ruby). For example:

new Date("1990-12-31T23:00:00Z")
// -> Tue Jan 01 1991 01:00:00 GMT+0200 (Eastern European Standard Time)

The input is parsed correctly, but it’s converted to local timezone. (Note that this loses the information of the timezone of the input value). Now if I want to format the date it will show wrong year etc. depending on my timezone. For example, if your computer is set to some other timezone than utc, then the following test will fail:

// test/integration/builtin/filters/date.ts

it('should not convert timezones', async function () {
  return test('{{ "1990-12-31T23:00:00Z" | date: "%Y-%m-%dT%H:%M:%S"}}', '1990-12-31T23:00:00')
})

[wyozi]

@petuomin imo the “conversion to the target timezone” is the difficult part. There is no easy way to convert to given timezone since it’s not as simple as addition (unless only numeric fixed offset timezones are supported, and even then DST might pose some problems). For instance, how would you modify the custom strftime to convert the given date to Asia/Shanghai timezone?

Taking advantage of Intl.DateTimeFormat would be an option, but as far as I can tell it would require a complete overhaul of strftime and add additional browser requirements. Maybe that’s the only way to have a “proper” timezone support though. The author of Luxon goes a bit deeper into this here.

It seems that one major issue here is the automatic conversion to local timezone. If the date filter just kept the dates and times the same (give timestamp with hour=20, get formatted string with hour=20), the issue would be partially solved. That’s why I suggested dropping timezone as one potential solution/workaround.

[harttle]

🎉 This issue has been resolved in version 9.19.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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