Cron Task type is not aware about local Timezone in the cron-string

[dmitriev-e]

Describe the bug
If you have Timezone configuration in the host system
(in my case I have timezone EEST

Wed Jul  2 13:00:44 EEST 2025

plus
if you have Timezone configuration in Django

Python 3.12.0 (v3.12.0:0fb18b02c8, Oct  2 2023, 09:45:56) [Clang 13.0.0 (clang-1300.0.29.30)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> from django.utils.timezone import get_current_timezone
>>> print(get_current_timezone())
Europe/Nicosia
>>> from django.utils.timezone import localtime 
>>> print(localtime())
2025-07-02 13:08:58.644141+03:00
>>>

but
In Database you store datetime in UTC format

+--------------------+---------------------+--------------------+
| @@global.time_zone | @@session.time_zone | @@system_time_zone |
+--------------------+---------------------+--------------------+
| SYSTEM             | SYSTEM              | UTC                |
+--------------------+---------------------+--------------------+
1 row in set (0.001 sec)

When you try to create a Cron-type task via build-in web-interface
with next cron-string
55 14 * * *

in DB we have next record (I converted it to JSON-format)

"scheduler_task": [
	{
		"id" : 9,
		"created_at" : "2025-07-02T06:53:11.558Z",
		"updated_at" : "2025-07-02T08:55:47.818Z",
		"name" : "sample_everyday_cron",
		"task_type" : "CronTaskType",
		"callable" : "scheduler.tests.jobs.test_args_kwargs",
		"enabled" : 1,
		"queue" : "default",
		"at_front" : 0,
		"timeout" : null,
		"result_ttl" : null,
		"failed_runs" : 0,
		"successful_runs" : 0,
		"last_successful_run" : null,
		"last_failed_run" : null,
		"interval" : null,
		"interval_unit" : "hours",
		"repeat" : null,
		"scheduled_time" : "2025-07-02T11:55:00.000Z",
		"cron_string" : "55 14 * * *",
		"job_name" : "default:9:20250702115016673618"
	}
]}

Ok - We have "scheduled_time" "2025-07-02T11:55:00.000Z" - is correct time in UTC format
but what about worker job ?
Let's check Redis

127.0.0.1:6379> ZRANGE :registry:default:scheduled_jobs 0 -1 WITHSCORES
1) "default:9:20250702115016673618"
2) "1751468100"

convert Timestamp 1751468100 to Date - 07/02/2025, 14:55:00 <<-- This is UTC datetime !!

So, In the end, we have next run at 07/02/2025, 14:55:00 in UTC time
It means - the real running will be at 17:55 in my case (UTC+3)

To Reproduce
Steps to reproduce the behavior:

1. Be sure, that you have another timezone on you PC (I have UTC+3)
2. Be sure that Worker is running
3. Create task-type "Cron Task"
4. Fill the cron-string , for example now+few hours
5. Go to /scheduler/queue/
6. Click to Scheduled Jobs count link in you queue (in my case - default queue)
7. Find new ID for the recently created task
8. Check column "Scheduled"
9. Check real time of real execution

Expected behavior
When I fill cron-string, I'm expecting executiong at specific time. Cron Task must to be aware about timezone.

Screenshots

Desktop (please complete the following information):

• OS: MacOS Sonoma
• python version - 3.12
• django version - 5.1.8

[dmitriev-e]

django-tasks-scheduler
last version 4.0.5

[dmitriev-e]

Hello. Any updates ?

[cunla]

Will look into it this week

[dmitriev-e]

I added few logs to
def get_next_cron_time()...

def get_next_cron_time(cron_string: Optional[str]) -> Optional[timezone.datetime]:
    """Calculate the next scheduled time by creating a crontab object with a cron string"""
    if cron_string is None:
        return None
    now = timezone.now()
    itr = croniter.croniter(cron_string, now)
    logger.debug(f"Cron string: {cron_string}, now: {now}, itr: {itr}")
    next_itr = itr.get_next(timezone.datetime)
    logger.debug(f"Next cron time: {next_itr}")
    return next_itr

What we receive from coniter().get_next(timezone.datetime)

DEBUG:scheduler:Cron string: 15 22 * * *, now: 2025-07-14 19:37:13.660442+00:00, itr: <croniter.croniter.croniter object at 0x77dfabef0620>
DEBUG:scheduler:Next cron time: 2025-07-14 22:15:00+00:00
DEBUG:scheduler:[Scheduler WINDOWS-42OIMNU-worker.2/1487027] Scheduler updating lock for queue default

[dmitriev-e]

scheduler.models.task Line 450
Seems we need to create now as timezone_aware object, for send this object to croniter

If change this line to
now = timezone.datetime.now(tz=timezone.get_current_timezone())
it fix the issue

[cunla]

Do you want to submit a PR to fix it?
Since you already did most of the work..

[cunla]

Do you have in your settings USE_TZ=True?

[dmitriev-e]

Do you have in your settings USE_TZ=True?

yes

Python 3.12.3 (main, Jun 18 2025, 17:59:45) [GCC 13.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> from django.conf import settings
>>> print(settings.USE_TZ)
True
>>> 

[cunla]

How about settings.TIME_ZONE?

[dmitriev-e]

How about settings.TIME_ZONE?

>>> from django.conf import settings
>>> print(settings.TIME_ZONE)
Europe/Nicosia
>>> 

UTC+3

Last fix didn't resolve the issue with start time in Redis (for Worker)

[cunla]

Should be fixed in the new release