Proposal: Duration

Isiah Meadows isiahmeadows at
Tue Mar 5 01:26:26 UTC 2019

Alexandre: I feel it's only *related* to dates and times:

- Dates and times refer to absolute points.
- Durations would refer to distances between two dates and/or times.

However, I do feel this should be discussed in And down this vein, I've
created just now.

Naveen: If you look at that proposal and particularly the issue I
filed, you can see date handling isn't as simple as it looks. There's
an entire database dedicated to localizing just times [1] (source:
[2]), and numeric date handling is a mess all on its own, [3] even if
you just stick with *just* the Gregorian calendar. [4] About the only
portable way to handle a date is to just do a bunch of UTC offsets to
the start of January 1, 1970, but even that has glitches in the form
of leap seconds. [5]

Or to put it simply: Date handling is hard.



Isiah Meadows
contact at

On Mon, Mar 4, 2019 at 4:30 PM Mark Davis ️ <mark at> wrote:
> Sadly, time is not that simple. Most people using calendars consider the duration between January 15 and March 15 to be exactly 2 months. But such intervals are a different number of days, hence milliseconds.
> Mark
> On Mon, Mar 4, 2019 at 11:21 AM Naveen Chawla <naveen.chwl at> wrote:
>> I don't like it. Duration is just milliseconds for me.
>> On Mon, 4 Mar 2019 at 18:47 Alexandre Morgaut <alexandre.morgaut at> wrote:
>>> Here a proposal to make ECMAScript natively support a Duration Object
>>> I talked about it a long time ago (2011) on the WHATWG mailing list in the context of the Timers API:
>>> l think that such a proposal would better take place in the core of the language and having worked on a framework date time APIs I tried to give this approach a better look.
>>> ECMAScript natively support Dates since its very first version
>>> It started to support the ISO 8601 string format in edition 5
>>> ( Date Time String Format )
>>> Durations like Dates can be very tricky, especially with I18n in mind, but the ECMA standard already had to be handled most of the Duration tricky part for the Date Object in EMCA 262 & ECMA 402.
>>> Duration, sometimes called TimeInterval, is a common concept supported by most languages or associated standard libs.
>>> In very short, Duration object would:
>>> - support the ISO syntax in its contructor: new Duration('P6W') // for  Period 6 Weeks
>>> - allow to handle Date diff operations
>>> - allow to be interpreted by setTimeout() & setInterval()
>>> Please find below a draft exposing the concept
>>> I'd be very happy if someone from TC39 would be interested to champion it
>>> Regards,
>>> Alexandre.
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