diff --git a/cylc/flow/flow_mgr.py b/cylc/flow/flow_mgr.py
index 6cb9b642633..e371318a383 100644
--- a/cylc/flow/flow_mgr.py
+++ b/cylc/flow/flow_mgr.py
@@ -93,31 +93,36 @@ def stringify_flow_nums(flow_nums: Set[int], full: bool = False) -> str:
 
     Examples:
         >>> stringify_flow_nums({})
-        '(none)'
+        '(flows=none)'
 
         >>> stringify_flow_nums({1})
         ''
 
         >>> stringify_flow_nums({1}, True)
-        '(1)'
+        '(flows=1)'
 
         >>> stringify_flow_nums({1,2,3})
-        '(1,2,3)'
+        '(flows=1,2,3)'
 
     """
     if not full and flow_nums == {1}:
         return ""
-    return (
-        "("
-        f"{','.join(str(i) for i in flow_nums) or 'none'}"
-        ")"
-    )
+    else:
+        return (
+            "(flows="
+            f"{','.join(str(i) for i in flow_nums) or 'none'}"
+            ")"
+        )
 
 
 class FlowMgr:
     """Logic to manage flow counter and flow metadata."""
 
-    def __init__(self, db_mgr: "WorkflowDatabaseManager", utc: bool) -> None:
+    def __init__(
+        self,
+        db_mgr: "WorkflowDatabaseManager",
+        utc: bool = True
+    ) -> None:
         """Initialise the flow manager."""
         self.db_mgr = db_mgr
         self.flows: Dict[int, Dict[str, str]] = {}
@@ -156,7 +161,7 @@ def get_flow_num(
                 )
         else:
             # Record a new flow.
-            now_sec = datetime.datetime.now(self._timezone).isoformat(
+            now_sec = datetime.datetime.now(tz=self._timezone).isoformat(
                 timespec="seconds"
             )
             meta = meta or "no description"
diff --git a/cylc/flow/scheduler.py b/cylc/flow/scheduler.py
index a15ff13ff50..09f25ecfff3 100644
--- a/cylc/flow/scheduler.py
+++ b/cylc/flow/scheduler.py
@@ -604,9 +604,6 @@ def log_start(self) -> None:
 
             # Note that the following lines must be present at the top of
             # the workflow log file for use in reference test runs.
-            LOG.info(
-                "Task log prefix: CYCLE/TASK[/JOB][(FLOWS)]:STATUS"
-            )
             LOG.info(
                 f'Run mode: {self.config.run_mode()}',
                 extra=RotatingLogFileHandler.header_extra
diff --git a/tests/functional/flow-triggers/13-noflow-nomerge.t b/tests/functional/flow-triggers/13-noflow-nomerge.t
index d380268e449..8dfa08f994c 100644
--- a/tests/functional/flow-triggers/13-noflow-nomerge.t
+++ b/tests/functional/flow-triggers/13-noflow-nomerge.t
@@ -27,7 +27,7 @@ run_ok "${TEST_NAME_BASE}-run" cylc play "${WORKFLOW_NAME}"
 poll_grep_workflow_log "Workflow stalled"
 
 run_ok "${TEST_NAME_BASE}-trigger" cylc trigger --flow=none "${WORKFLOW_NAME}//1/a"
-poll_grep_workflow_log -E "1/a/02\(none\):running.*=> succeeded"
+poll_grep_workflow_log -E "1/a/02\(flows=none\):running.*=> succeeded"
 
 cylc stop --now --now --max-polls=5 --interval=2 "$WORKFLOW_NAME"
 
diff --git a/tests/functional/restart/50-two-flows/flow.cylc b/tests/functional/restart/50-two-flows/flow.cylc
index 1181e4e80cb..bd9de46c8b4 100644
--- a/tests/functional/restart/50-two-flows/flow.cylc
+++ b/tests/functional/restart/50-two-flows/flow.cylc
@@ -23,7 +23,7 @@
            if ((CYLC_TASK_FLOW_NUMBERS == 1)); then
                cylc trigger --flow=new --meta="cheese wizard" \
                    "$CYLC_WORKFLOW_ID//1/a"
-               cylc__job__poll_grep_workflow_log -E "\[1/a/02\(2\):submitted\] => running"
+               cylc__job__poll_grep_workflow_log -E "\[1/a/02\(flows=2\):submitted\] => running"
                cylc stop $CYLC_WORKFLOW_ID
            fi
        """
diff --git a/tests/unit/test_flow_mgr.py b/tests/unit/test_flow_mgr.py
index 52d865e861b..c9171b02073 100644
--- a/tests/unit/test_flow_mgr.py
+++ b/tests/unit/test_flow_mgr.py
@@ -26,6 +26,7 @@
 
 
 FAKE_NOW = datetime.datetime(2020, 12, 25, 17, 5, 55)
+FAKE_NOW_ISO = FAKE_NOW.isoformat()
 
 
 @pytest.fixture
@@ -33,7 +34,7 @@ def patch_datetime_now(monkeypatch):
 
     class mydatetime:
         @classmethod
-        def now(cls):
+        def now(cls, tz=None):
             return FAKE_NOW
 
     monkeypatch.setattr(datetime, 'datetime', mydatetime)
@@ -49,41 +50,40 @@ def test_all(
     flow_mgr = FlowMgr(db_mgr)
     caplog.set_level(logging.INFO, CYLC_LOG)
 
-    # automatic: expect flow number 1
     meta = "the quick brown fox"
     assert flow_mgr.get_flow_num(None, meta) == 1
-    msg1 = f"flow: 1 ({meta}) {FAKE_NOW}"
+    msg1 = f"flow: 1 ({meta}) {FAKE_NOW_ISO}"
     assert f"New {msg1}" in caplog.messages
 
     # automatic: expect 2
     meta = "jumped over the lazy dog"
     assert flow_mgr.get_flow_num(None, meta) == 2
-    msg2 = f"flow: 2 ({meta}) {FAKE_NOW}"
+    msg2 = f"flow: 2 ({meta}) {FAKE_NOW_ISO}"
     assert f"New {msg2}" in caplog.messages
 
     # give flow 2: not a new flow
     meta = "jumped over the moon"
     assert flow_mgr.get_flow_num(2, meta) == 2
-    msg3 = f"flow: 2 ({meta}) {FAKE_NOW}"
+    msg3 = f"flow: 2 ({meta}) {FAKE_NOW_ISO}"
     assert f"New {msg3}" not in caplog.messages
     assert f"Ignoring flow metadata \"{meta}\": 2 is not a new flow" in caplog.messages
 
     # give flow 4: new flow
     meta = "jumped over the cheese"
     assert flow_mgr.get_flow_num(4, meta) == 4
-    msg4 = f"flow: 4 ({meta}) {FAKE_NOW}"
+    msg4 = f"flow: 4 ({meta}) {FAKE_NOW_ISO}"
     assert f"New {msg4}" in caplog.messages
 
     # automatic: expect 3
     meta = "jumped over the log"
     assert flow_mgr.get_flow_num(None, meta) == 3
-    msg5 = f"flow: 3 ({meta}) {FAKE_NOW}"
+    msg5 = f"flow: 3 ({meta}) {FAKE_NOW_ISO}"
     assert f"New {msg5}" in caplog.messages
 
     # automatic: expect 5 (skip over 4)
     meta = "crawled under the log"
     assert flow_mgr.get_flow_num(None, meta) == 5
-    msg6 = f"flow: 5 ({meta}) {FAKE_NOW}"
+    msg6 = f"flow: 5 ({meta}) {FAKE_NOW_ISO}"
     assert f"New {msg6}" in caplog.messages
     flow_mgr._log()
     assert (