diff --git a/frontend/packages/swarm-ui/src/util.ts b/frontend/packages/swarm-ui/src/util.ts
index 6aec3416..577b8b88 100644
--- a/frontend/packages/swarm-ui/src/util.ts
+++ b/frontend/packages/swarm-ui/src/util.ts
@@ -1,15 +1,19 @@
 // Small pure render helpers shared across swarm-ui pages. Not folded
-// into `@hive/shared` — these are swarm-ui's own formatting choices
-// (compact, one unit deep), not a cross-package contract, and the
-// dashboard package already has its own near-identical `fmtAgo` in
-// `util.js` for the same reason: two small vanilla-vs-Preact call
-// sites don't justify a shared abstraction over a five-line function.
+// into `@hive/shared` — swarm-ui's formatting choices aren't a
+// cross-package contract, and there's nothing here worth sharing.
+
+// Relative age, coarsened to one unit ("5m ago"). Built on the native
+// `Intl.RelativeTimeFormat` (no dependency needed — mara asked whether
+// a lightweight package was warranted; the runtime already ships this)
+// with `style: 'narrow'`, which produces the same "5s/5m/5h/5d ago"
+// shape the dashboard package's hand-rolled equivalent does, verified
+// against a real `Intl` call rather than assumed from the spec.
+const RTF = new Intl.RelativeTimeFormat('en', { numeric: 'always', style: 'narrow' });
 
-// Relative age in whole seconds, coarsened to one unit ("5m ago").
 export function fmtAgo(ageSeconds: number): string {
   const age = Math.max(0, Math.floor(ageSeconds));
-  if (age < 60) return age + 's ago';
-  if (age < 3600) return Math.floor(age / 60) + 'm ago';
-  if (age < 86400) return Math.floor(age / 3600) + 'h ago';
-  return Math.floor(age / 86400) + 'd ago';
+  if (age < 60) return RTF.format(-age, 'second');
+  if (age < 3600) return RTF.format(-Math.floor(age / 60), 'minute');
+  if (age < 86400) return RTF.format(-Math.floor(age / 3600), 'hour');
+  return RTF.format(-Math.floor(age / 86400), 'day');
 }