I wonder if this'd be better addressed as some sort of mediawiki-wide fix? Anything with e.g. <span class="mw-relative-time" data-ts="123443432"> would get updated by some site-wide JS, extensions and pages wouldn't need to independently implement it, and users wouldn't have to remember which pages have this behavior and which don't...

A core solution might be helpful, I don't know where getHumanTimestamp is used. I think there is an existing issue in that the JS library used is not identical to the PHP library.

In T310194#7989650, @DLynch wrote:

Anything with e.g. <span class="mw-relative-time" data-ts="123443432"> would get updated by some site-wide JS

As far as I remember, moment.js is quite a heavy library, so automagically including it may have unwanted performance consequences (especially as <span class="mw-relative-time" data-ts="123443432"> can be added by unprivileged users to the parser output).

In T310194#7989938, @Esanders wrote:

A core solution might be helpful, I don't know where getHumanTimestamp is used. I think there is an existing issue in that the JS library used is not identical to the PHP library.

getHumanTimestamp currently outputs plain text, and this may be assumed by callers (e.g. ad5a7f50 includes it in an API result, and the consumer added in f9aac368 escapes it before adding to the page). If we want it to output machine-readable data for moment.js, it should be a new method or an optional parameter to the existing method (the implicit plain text output may be deprecated afterwards, but it does need to go through the deprecation process).

data-ts="123443432"> can be added by unprivileged users to the parser output

That can be fixed by using data-mw-ts