diff --git a/apps/web/src/components/pullRequest/PullRequestsPage.tsx b/apps/web/src/components/pullRequest/PullRequestsPage.tsx
index 4c72a9cd6ebe..26e672ebbfb5 100644
--- a/apps/web/src/components/pullRequest/PullRequestsPage.tsx
+++ b/apps/web/src/components/pullRequest/PullRequestsPage.tsx
@@ -44,6 +44,7 @@ import {
   pullRequestOverrideAfterAction,
   reusePullRequestEntries,
   settlePullRequestOverrides,
+  comparePullRequestsByRecency,
   largestPullRequestReadCount,
 } from "./pullRequestList.logic";
 import {
@@ -560,7 +561,7 @@ export function PullRequestsPage() {
       const held = new Set(ordered.entries.map(pullRequestEntryKey));
       const arrived = answered.entries.filter((entry) => !held.has(pullRequestEntryKey(entry)));
       const appended = rankPullRequestMatches(
-        arrived.toSorted((left, right) => right.updatedAt.localeCompare(left.updatedAt)),
+        arrived.toSorted(comparePullRequestsByRecency),
         sentParsed.text,
       );
       setOrdered({ key: filterKey, source: answered, entries: [...ordered.entries, ...appended] });
diff --git a/apps/web/src/components/pullRequest/pullRequestDetail.logic.test.ts b/apps/web/src/components/pullRequest/pullRequestDetail.logic.test.ts
index ad7e99ecf87e..f00757b37dea 100644
--- a/apps/web/src/components/pullRequest/pullRequestDetail.logic.test.ts
+++ b/apps/web/src/components/pullRequest/pullRequestDetail.logic.test.ts
@@ -313,6 +313,19 @@ describe("review verdicts", () => {
 });
 
 describe("pull request timeline", () => {
+  it("orders host timestamps by instant across offsets and fractional seconds", () => {
+    const events = buildPullRequestTimeline({
+      ...TIMELINE_SOURCE,
+      createdAt: "2026-07-05T01:00:00+02:00",
+      commits: [{ oid: "commit", messageHeadline: "", committedDate: "2026-07-05T00:30:00Z" }],
+      comments: [{ ...TIMELINE_SOURCE.comments[0]!, createdAt: "2026-07-05T00:30:00.5Z" }],
+      mergedAt: null,
+      closedAt: null,
+    });
+
+    expect(events.map((event) => event.id)).toEqual(["c1", "commit", "created"]);
+  });
+
   it("drops a body that is nothing but a bot's HTML comment, and keeps one that says more", () => {
     const events = buildPullRequestTimeline({
       ...TIMELINE_SOURCE,
diff --git a/apps/web/src/components/pullRequest/pullRequestDetail.logic.ts b/apps/web/src/components/pullRequest/pullRequestDetail.logic.ts
index b4d7a7052163..3146fe39fab1 100644
--- a/apps/web/src/components/pullRequest/pullRequestDetail.logic.ts
+++ b/apps/web/src/components/pullRequest/pullRequestDetail.logic.ts
@@ -762,7 +762,7 @@ export function buildPullRequestTimeline(
           },
         ]
       : []),
-  ].toSorted((left, right) => right.at.localeCompare(left.at));
+  ].toSorted((left, right) => (instant(right.at) || 0) - (instant(left.at) || 0));
 }
 
 const FINDING_LIMIT = 20;
diff --git a/apps/web/src/components/pullRequest/pullRequestList.logic.test.ts b/apps/web/src/components/pullRequest/pullRequestList.logic.test.ts
index 7bbc0c3ab0a6..6685095b5774 100644
--- a/apps/web/src/components/pullRequest/pullRequestList.logic.test.ts
+++ b/apps/web/src/components/pullRequest/pullRequestList.logic.test.ts
@@ -468,6 +468,20 @@ describe("merging the environments' own listings", () => {
       ...overrides,
     }) as Parameters<typeof mergePullRequestLists>[0][number][1];
 
+  it("orders host timestamps by instant across offsets and fractional seconds", () => {
+    const entries = [
+      entry({ number: 1, updatedAt: "2026-07-05T01:00:00+02:00" }),
+      entry({ number: 2, updatedAt: "2026-07-05T00:30:00Z" }),
+      entry({ number: 3, updatedAt: "2026-07-05T00:30:00.5Z" }),
+    ];
+    const merged = mergePullRequestLists([
+      [ENV_1, answer({ entries: entries.slice(0, 2) })],
+      [ENV_2, answer({ entries: entries.slice(2) })],
+    ]);
+
+    expect(merged?.entries.map((row) => row.number)).toEqual([3, 2, 1]);
+  });
+
   it("tags every row with the environment that read it, newest first", () => {
     const merged = mergePullRequestLists([
       [ENV_1, answer({ entries: [entry({ number: 1, updatedAt: "2026-07-01T00:00:00Z" })] })],
diff --git a/apps/web/src/components/pullRequest/pullRequestList.logic.ts b/apps/web/src/components/pullRequest/pullRequestList.logic.ts
index 3d996b2e82be..6bb3dfd600a2 100644
--- a/apps/web/src/components/pullRequest/pullRequestList.logic.ts
+++ b/apps/web/src/components/pullRequest/pullRequestList.logic.ts
@@ -404,11 +404,16 @@ export function partitionPullRequestsWithPriority<Entry extends PullRequestListE
       others.push(entry);
     }
   }
-  const byRecency = (left: Entry, right: Entry) => right.updatedAt.localeCompare(left.updatedAt);
   return (
     [
-      { key: "authored", entries: [...authoredByKey.values()].toSorted(byRecency) },
-      { key: "reviewRequested", entries: [...reviewByKey.values()].toSorted(byRecency) },
+      {
+        key: "authored",
+        entries: [...authoredByKey.values()].toSorted(comparePullRequestsByRecency),
+      },
+      {
+        key: "reviewRequested",
+        entries: [...reviewByKey.values()].toSorted(comparePullRequestsByRecency),
+      },
       { key: "others", entries: others },
     ] as const
   )
@@ -503,7 +508,7 @@ export function mergePullRequestLists(
   return {
     viewers,
     providers: [...providers.values()],
-    entries: entries.toSorted((left, right) => right.updatedAt.localeCompare(left.updatedAt)),
+    entries: entries.toSorted(comparePullRequestsByRecency),
     errors,
     truncated,
     nextCursors,
@@ -697,7 +702,7 @@ export function rankPullRequestMatches<Entry extends PullRequestListEntry>(
   if (query.trim().length === 0) return entries;
   return entries.toSorted((left, right) => {
     const byScore = scorePullRequestMatch(right, query) - scorePullRequestMatch(left, query);
-    return byScore !== 0 ? byScore : right.updatedAt.localeCompare(left.updatedAt);
+    return byScore !== 0 ? byScore : comparePullRequestsByRecency(left, right);
   });
 }
 
@@ -718,24 +723,29 @@ export function rankPullRequestsByMergeReadiness<Entry extends PullRequestListEn
     if (byTier !== 0) return byTier;
     const measured = Number(hasMeasuredSize(right)) - Number(hasMeasuredSize(left));
     const sized = left.additions + left.deletions - (right.additions + right.deletions);
-    return measured || sized || right.updatedAt.localeCompare(left.updatedAt);
+    return measured || sized || comparePullRequestsByRecency(left, right);
   });
 }
 
+export function comparePullRequestsByRecency(
+  left: PullRequestListEntry,
+  right: PullRequestListEntry,
+) {
+  const leftUpdated = toSortableTimestamp(left.updatedAt);
+  const rightUpdated = toSortableTimestamp(right.updatedAt);
+  const measured = Number(leftUpdated === null) - Number(rightUpdated === null);
+  if (measured !== 0) return measured;
+  if (leftUpdated === null || rightUpdated === null) return 0;
+  return rightUpdated - leftUpdated;
+}
+
 function rankByTierThenRecency<Entry extends PullRequestListEntry>(
   entries: ReadonlyArray<Entry>,
   tier: (entry: Entry) => number,
 ): ReadonlyArray<Entry> {
-  const timestamp = (entry: Entry) => toSortableTimestamp(entry.updatedAt);
   return entries.toSorted((left, right) => {
     const byTier = tier(left) - tier(right);
-    if (byTier !== 0) return byTier;
-    const leftUpdated = timestamp(left);
-    const rightUpdated = timestamp(right);
-    const measured = Number(leftUpdated === null) - Number(rightUpdated === null);
-    if (measured !== 0) return measured;
-    if (leftUpdated === null || rightUpdated === null) return 0;
-    return rightUpdated - leftUpdated;
+    return byTier !== 0 ? byTier : comparePullRequestsByRecency(left, right);
   });
 }
 
diff --git a/apps/web/src/components/pullRequest/pullRequestListGroups.logic.ts b/apps/web/src/components/pullRequest/pullRequestListGroups.logic.ts
index 62a3200a6663..f1417a21eec2 100644
--- a/apps/web/src/components/pullRequest/pullRequestListGroups.logic.ts
+++ b/apps/web/src/components/pullRequest/pullRequestListGroups.logic.ts
@@ -7,6 +7,7 @@ import type {
 import type { PullRequestTabStatusSeed } from "~/components/RightPanelTabs";
 import { pullRequestSurfaceId } from "~/rightPanelStore";
 import {
+  comparePullRequestsByRecency,
   filterPullRequestsByInvolvement,
   groupPullRequestsByInvolvement,
   matchesPullRequestFilters,
@@ -68,9 +69,7 @@ export function pullRequestGroups({
         )
       : involvementEntries;
     if (text.length === 0) {
-      return narrowedEntries.toSorted((left, right) =>
-        right.updatedAt.localeCompare(left.updatedAt),
-      );
+      return narrowedEntries.toSorted(comparePullRequestsByRecency);
     }
     return narrowedEntries.filter(
       (entry) =>