diff --git a/tests/source/recorder.py b/tests/source/recorder.py
index 531d5fe..9fbab4c 100644
--- a/tests/source/recorder.py
+++ b/tests/source/recorder.py
@@ -229,19 +229,32 @@ def first_sync_config(owner: str, name: str) -> TrackingConfig:
 
 
 async def record_first_sync(
-    token: str, owner: str, name: str, *, inner: httpx.AsyncBaseTransport | None = None
+    token: str,
+    owner: str,
+    name: str,
+    *,
+    inner: httpx.AsyncBaseTransport | None = None,
+    clock: Clock | None = None,
 ) -> list[Unit]:
     """Run a first sync of ``owner/name`` into a scratch database through the recording
     transport; every unit it asked for. A private repository is refused after the sync's resolve
     (its label pages included) and before any other request; a failed item or a run that does not
-    exit 0 stops it too."""
+    exit 0 stops it too.
+
+    ``clock`` is the run's clock, the system clock by default. A replay of recorded units passes a
+    fixed one: the sync's 24-hour refresh measures each account from its recorded ``Date``, so on
+    the system clock a replay asks for lookups the recording does not hold once a day has
+    passed."""
     _refuse_listed(owner, name)
+    run_clock = clock or SystemClock()
     recorded_at = datetime.now(UTC).strftime("%Y-%m-%dT%H:%M:%SZ")
     recording = RecordingTransport(inner or httpx.AsyncHTTPTransport(), recorded_at)
     opened: list[PublicOnlySource] = []
 
     def open_source(deadline: datetime | None) -> PublicOnlySource:
-        opened.append(PublicOnlySource(token, http_transport=recording, deadline=deadline))
+        opened.append(
+            PublicOnlySource(token, http_transport=recording, clock=run_clock, deadline=deadline)
+        )
         return opened[-1]
 
     config = first_sync_config(owner, name)
@@ -256,7 +269,7 @@ def open_source(deadline: datetime | None) -> PublicOnlySource:
                 code_version="recorder",
             ),
             open_source=open_source,
-            clock=SystemClock(),
+            clock=run_clock,
         )
     # The engine fails the run on the refusal, before the index.
     refused = [source.refused for source in opened if source.refused is not None]
diff --git a/tests/source/test_recorder.py b/tests/source/test_recorder.py
index e06566d..af89084 100644
--- a/tests/source/test_recorder.py
+++ b/tests/source/test_recorder.py
@@ -125,7 +125,9 @@ async def test_a_listed_private_repository_is_never_requested(owner: str, name:
     with pytest.raises(PrivateRepository):
         await record("test-token", inner=replay.transport(), scenarios=scenarios)
     with pytest.raises(PrivateRepository):
-        await record_first_sync("test-token", owner, name, inner=replay.transport())
+        await record_first_sync(
+            "test-token", owner, name, inner=replay.transport(), clock=FakeClock()
+        )
     assert replay.seen == []
 
 
@@ -278,7 +280,9 @@ async def test_recording_a_first_sync_of_its_recordings_gives_them_back() -> Non
     """The first sync asks for exactly the recorded units, and records each as it was."""
     replay = Replay.from_directory(FIRST_SYNC)
     owner, name = FIRST_SYNC_REPOSITORY
-    units = await record_first_sync("test-token", owner, name, inner=replay.transport())
+    units = await record_first_sync(
+        "test-token", owner, name, inner=replay.transport(), clock=FakeClock()
+    )
     assert replay.problems == []
     # One resolve, the sync's own: the resolution the privacy check reads is the one it uses.
     assert [seen.operation for seen in replay.seen] == [
@@ -306,7 +310,9 @@ async def test_a_private_repository_stops_a_first_sync_after_its_resolve() -> No
     unit.data["isPrivate"] = True
     replay.add(unit)
     with pytest.raises(PrivateRepository, match=f"{owner}/{name}"):
-        await record_first_sync("test-token", owner, name, inner=replay.transport())
+        await record_first_sync(
+            "test-token", owner, name, inner=replay.transport(), clock=FakeClock()
+        )
     assert [seen.operation for seen in replay.seen] == ["Resolve"]
 
 
@@ -318,7 +324,9 @@ async def test_a_retried_item_records_one_unit_per_file(first_sync: bool) -> Non
     replay.modify(_batch_alias_error, when=lambda seen: seen.operation == "PullRequestBatch")
     if first_sync:
         owner, name = FIRST_SYNC_REPOSITORY
-        units = await record_first_sync("test-token", owner, name, inner=replay.transport())
+        units = await record_first_sync(
+            "test-token", owner, name, inner=replay.transport(), clock=FakeClock()
+        )
     else:
         units = await record("test-token", inner=replay.transport())
     batches = [seen.numbers for seen in replay.seen if seen.operation == "PullRequestBatch"]
@@ -371,7 +379,9 @@ async def test_a_first_sync_that_fails_names_why(
     change(replay)
     owner, name = FIRST_SYNC_REPOSITORY
     with pytest.raises(RecordingFailed) as raised:
-        await record_first_sync("test-token", owner, name, inner=replay.transport())
+        await record_first_sync(
+            "test-token", owner, name, inner=replay.transport(), clock=FakeClock()
+        )
     assert str(raised.value) == message
     assert [seen.operation for seen in replay.seen] == ["Resolve"]
 
@@ -383,13 +393,17 @@ async def test_a_first_sync_that_does_not_exit_0_stops_the_recording() -> None:
     )
     owner, name = FIRST_SYNC_REPOSITORY
     with pytest.raises(RecordingFailed, match="first sync exited 2"):
-        await record_first_sync("test-token", owner, name, inner=replay.transport())
+        await record_first_sync(
+            "test-token", owner, name, inner=replay.transport(), clock=FakeClock()
+        )
 
 
 def _first_sync_units() -> list[Any]:
     owner, name = FIRST_SYNC_REPOSITORY
     replay = Replay.from_directory(FIRST_SYNC)
-    return asyncio.run(record_first_sync("test-token", owner, name, inner=replay.transport()))
+    return asyncio.run(
+        record_first_sync("test-token", owner, name, inner=replay.transport(), clock=FakeClock())
+    )
 
 
 @pytest.mark.parametrize("oversized", [False, True])