From 654516400df4c7339332bac3f30f8fd23d74329e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=88=98=E4=BA=AC=E5=9D=A4?= <2802629917@qq.com>
Date: Sat, 24 Oct 2026 15:06:23 +0800
Subject: [PATCH] fix(cron): use elapsed time across daylight-saving
 transitions

---
 reme/components/job/cron_job.py |  3 ++-
 tests/unit/test_cron_delay.py   | 40 +++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 1 deletion(-)
 create mode 100644 tests/unit/test_cron_delay.py

diff --git a/reme/components/job/cron_job.py b/reme/components/job/cron_job.py
index 71948597..466d607f 100644
--- a/reme/components/job/cron_job.py
+++ b/reme/components/job/cron_job.py
@@ -32,7 +32,8 @@ class CronJob(BackgroundJob):
         from croniter import croniter
 
         nxt = croniter(self.cron_expr, now).get_next(datetime.datetime)
-        return max(0.0, (nxt - now).total_seconds())
+        # A wait needs elapsed seconds, including any intervening UTC-offset change.
+        return max(0.0, nxt.timestamp() - now.timestamp())
 
     async def _execute_steps(self) -> Response:
         context = RuntimeContext(**self.kwargs)
diff --git a/tests/unit/test_cron_delay.py b/tests/unit/test_cron_delay.py
new file mode 100644
index 00000000..b5d14965
--- /dev/null
+++ b/tests/unit/test_cron_delay.py
@@ -0,0 +1,40 @@
+"""Cron waits use elapsed seconds across timezone offset changes."""
+
+# pylint: disable=protected-access,missing-function-docstring,missing-class-docstring
+
+import datetime
+from types import SimpleNamespace
+
+import pytest
+
+from reme.components.job import cron_job as cron_job_module
+from reme.components.job.cron_job import CronJob
+
+
+@pytest.mark.parametrize(
+    "timezone,instant,expected_delay",
+    [
+        ("America/New_York", "2026-03-08T06:30:00+00:00", 1800),
+        ("America/New_York", "2026-11-01T04:30:00+00:00", 12600),
+        ("Europe/London", "2026-03-29T00:30:00+00:00", 5400),
+        ("Europe/London", "2026-10-25T00:30:00+00:00", 9000),
+        ("Australia/Lord_Howe", "2026-10-03T15:00:00+00:00", 3600),
+        ("Australia/Lord_Howe", "2026-04-04T13:30:00+00:00", 10800),
+        ("America/New_York", "2026-01-15T06:30:00+00:00", 5400),
+        ("Asia/Shanghai", "2026-03-07T17:30:00+00:00", 5400),
+        (None, "2026-01-15T01:30:00+00:00", 5400),
+    ],
+)
+def test_cron_delay_uses_elapsed_seconds(monkeypatch, timezone, instant, expected_delay):
+    fixed = datetime.datetime.fromisoformat(instant)
+
+    class FixedDatetime(datetime.datetime):
+        @classmethod
+        def now(cls, tz=None):
+            return fixed.astimezone(tz) if tz else fixed.replace(tzinfo=None)
+
+    monkeypatch.setattr(cron_job_module, "datetime", SimpleNamespace(datetime=FixedDatetime))
+    job = CronJob(cron="0 3 * * *")
+    job.app_context = SimpleNamespace(app_config=SimpleNamespace(timezone=timezone))
+
+    assert job._next_fire_delay() == expected_delay