Agree, when they are archived like in (google or web.archive.org), they will be relative to the indexing date if the label isn't calculated in client side, probably the javascript won't be working well in archive though.

Plus, consider using time tag, datetime attribute for displaying dates in a more accessible way. https://developer.mozilla.org/en-US/docs/Web/HTML/Element/ti... It's not so much different than a span tag in browsers yet, but why not making out webpages future compatible.