V0lantis opened a new issue, #35558:
URL: https://github.com/apache/airflow/issues/35558
### Apache Airflow version
Other Airflow 2 version (please specify below)
### What happened
After the time shift which happen in Europe during the last 29th morning of
October, we noticed that some of our dag we specific cron timetable were not
scheduling anymore.
The dag definition is as follow:
```python
with DAG(
dag_id="dag_id",
schedule="0 7-21 * * *",
max_active_runs=1,
) as dag:
```
with the following `start_date`
```python
start_date = timezone.parse("2022-04-26", "Europe/Paris")
```
### What you think should happen instead
The scheduler should have been able to continue scheduling new dag run
normally.
### How to reproduce
I created the following tests, to be able to dig into the issue. I will try
to implement a better one soon
```py
from __future__ import annotations
from pendulum import DateTime
from pendulum.tz.timezone import UTC
from airflow.timetables._cron import CronMixin
class TestCronMixin:
def test_get_next_true(self):
cron_mixin = CronMixin("0 7-21 * * *", timezone="Europe/Paris")
print("\n")
for day, hour in [(28, 20), (28, 21), (28, 22), (28, 23), (29, 0),
(29, 1), (29, 2), (29, 3), (29, 4), (29, 5), (29, 6), (29, 7)]:
date = DateTime(year=2023, month=10, day=day, hour=hour,
minute=0, second=0, tzinfo=UTC)
align_prev_date = cron_mixin._align_to_prev(date)
print(f"the {day} at {hour}: pre_date={align_prev_date}")
```
### Operating System
NAME="Amazon Linux" VERSION="2" ID="amzn" ID_LIKE="centos rhel fedora"
VERSION_ID="2" PRETTY_NAME="Amazon Linux 2" ANSI_COLOR="0;33"
CPE_NAME="cpe:2.3:o:amazon:amazon_linux:2" HOME_URL="https://amazonlinux.com/";
SUPPORT_END="2025-06-30"
### Versions of Apache Airflow Providers
```shell
$ pip freeze | grep providers
apache-airflow-providers-amazon==8.3.1
apache-airflow-providers-celery==3.2.1
apache-airflow-providers-cncf-kubernetes==7.4.2
apache-airflow-providers-common-sql==1.6.0
apache-airflow-providers-datadog==3.3.1
apache-airflow-providers-docker==3.7.1
apache-airflow-providers-ftp==3.4.2
apache-airflow-providers-github==2.3.1
apache-airflow-providers-google==10.3.0
apache-airflow-providers-hashicorp==3.5.0
apache-airflow-providers-http==4.4.2
apache-airflow-providers-imap==3.2.2
apache-airflow-providers-mysql==5.1.1
apache-airflow-providers-postgres==5.5.2
apache-airflow-providers-redis==3.4.0
apache-airflow-providers-salesforce==5.4.1
apache-airflow-providers-sftp==4.3.1
apache-airflow-providers-slack==7.3.1
apache-airflow-providers-sqlite==3.5.0
apache-airflow-providers-ssh==3.7.1
apache-airflow-providers-tableau==4.2.1
apache-airflow-providers-zendesk==4.3.1
```
### Deployment
Official Apache Airflow Helm Chart
### Deployment details
Kubernetes deployment
### Anything else
This problem will probably occurs every time we will experience the winter
time shift.
Luckily, we mitigate the issue by putting `catchup=False` to those dags
which didn't needed to catchup (obviously), but if we did need to have a proper
history for every hour, I don't know how we could have deal with this.
### Are you willing to submit PR?
- [X] Yes I am willing to submit a PR!
### Code of Conduct
- [X] I agree to follow this project's [Code of
Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)
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