Cron job "0 * * * *" does not run correctly, executions do not respect the scheduled time

[Angelk90]

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Bug

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Link: Test_workflows

I have configured a cron job in my GitHub Actions workflow to run a certain action every hour, at minute 0 (e.g. 0 * * * *), but I noticed that it does not run as expected.

My workflow should run every hour at minute 0, but I noticed that it runs at unexpected times, such as:

12:38
13:24
14:14

This does not seem to match the schedule 0 * * * *, which should run the job at minute 0 of every hour.

name: Cron

on:
  workflow_dispatch:
  schedule:
    - cron: '0 * * * *'

jobs:
  update-readme:
    runs-on: ubuntu-latest

    steps:
    - name: Checkout repository
      uses: actions/checkout@v3
...

What I expect:
00:00
01:00
02:00
03:00
...
23:00

Result:

Has anyone had similar experiences with cron jobs on GitHub Actions not respecting the scheduled time?

Could you confirm if the UTC time zone could be the cause of the issue and if there are any workarounds to make the cron job match the local time?

Could it be a problem with the machine?

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[Barmanji]

Probably is caused due to the cron process when handling scheduled workflows in GitHub Actions; such works are scheduled by the Github in the UTC time, despite all this, execution does run a little longer in various other reasons:

1. System Load: GitHub Actions runs the workflows in a shared environment. When the system is overloaded, scheduled workflows may queue to be run later than scheduled.

2. Time Drift The natural workflow does not actually begin on time. Perhaps there's a difference in time at which the workflow is actually taken up; therefore you may have had some execution times.

3. Configuration Errors The cron expression is wrong or misconfigured in the filename for the workflow.

Test and Debugging Steps

1. Verify your cron expression
   Remember to make a closer inspection of the cron syntax in the workflow file. An expression like 0 * * * * should run at minute 0 of every hour.

Example:
Dead
on:
schedule:

• cron: ' 0 * * * *
  `

2. Check GitHub Actions Logs:
   Check the workflow logs that have been executed. Look for a pattern or reason for delay. Check and look for queue messages related to the time taken to execute the workflow.

3. Account for UTC Time: GitHub Actions schedules are in UTC time. So, if you're not from that time zone, then make sure your expectation is in sync with UTC.

4. No procrastination.

You can't avoid load-induced delays but will reduce the impact of them if your workflow operates at less-populated times. For example, the one below may reduce contention, for instance, by using 3 * * * * instead of 0 * * * *.

5. Utilize Debugger Tools:

Include your workflow with timestamps or logging to track the actual start time of the workflow. 6. Check GitHub Support: In case of serious and persistent delays, please contact GitHub support with the information about your issue. ### Note on the Accuracy Scheduled GitHub Actions workflows do not have high-precision timing. If such pinpoint intervals are needed, consider such alternatives as an external cron job service using either AWS Lambda or Google Cloud Scheduler, which can fire off GitHub Actions using the REST API.

[Angelk90]

@Barmanji : Some actions were also skipped.