Relative timestamps like "3 weeks ago" or "4 months ago" make the activity feeds feel stale and dying. Even when members are actively posting. I have had a fair amount of feedback from ex-members who canceled because they felt there wasn't anything happening, even People post 3-4 times a week.
Giving us the option to display exact dates like "Posted April 1st" reframes the perception of the activity feed in the community.
Facebook, LinkedIn, and every major social platform uses this to keep users engaged longer, and I believe it would do the same for all of us.
To avoid disrupting existing communities, maybe you can ship this with a setting / toggle in the admin panel (Relative vs. Exact Date) so everyone can pick what works for them without forcing them into any changes.
I believe this would result in higher retention, better engagement, lower cancellations, and a community that looks alive to every new member who joins.
I included a screenshot from facebook for reference.