RelativeTimeFormat should support compound units

[sffc]

We got the following feature request from a Google Search client:

I'm working on a feature … that answers [what time will it be in X minutes/hours].

The UI spec calls for adding a phrase such as "one hour 20 minutes ago" or "in 45 minutes" to the template. In my use case I will have a timestamp for the "current time" … and the number of minutes relative to that that time.

What's the best way to format a relative timespan, such as "one hour 20 minutes ago" … ?

Backlink: https://yaqs.corp.google.com/eng/q/6499139655958528

Upstream: CLDR-14144

Also see: tc39/proposal-intl-duration-format#29

CC @younies

[ryzokuken]

The best way to move forward with this is to pursue the current plan of adding Temporal.Duration support for Intl.RelativeTimeFormat

[FrankYFTang]

Additional idea is to add a reference time other than "now".

[FrankYFTang]

It seems a good idea to champion a new proposal for Intl.RelativeTimeFormat v2 to enhance it for such a feature. I can also see additional different use case to use a different reference time for Intl.RelativeTimeFormat , such as "2 days after December 7, 1941" or "5 days, 23 hours, 54 minutes, and 41 seconds after April 11, 1970, 19:13:00 UTC"

[ryzokuken]

@FrankYFTang do you think this would still be relevant after DurationFormat lands?

[sffc]

This issue is for a different proposal. DurationFormat only formats "floating" durations. It does not format durations relative to a point in time. See tc39/proposal-intl-duration-format#29 (comment) for some discussion on the differences between these formats.