@app.function(schedule=modal.Period(days=1)) def daily_job(): print("Running daily task")


Activate with: `modal deploy script.py`

## Schedule Types

### Period (interval-based)

Runs at fixed intervals from the time of deployment:

```python
@app.function(schedule=modal.Period(hours=5))
def every_five_hours():
    ...

@app.function(schedule=modal.Period(minutes=30))
def half_hourly():
    ...

Redeployment resets the Period timer.

Cron (cron syntax)

Runs at specific times using cron expressions:

# 8 AM UTC every Monday
@app.function(schedule=modal.Cron("0 8 * * 1"))
def weekly_report():
    ...

# 6 AM New York time daily
@app.function(schedule=modal.Cron("0 6 * * *", timezone="America/New_York"))
def morning_report():
    ...

Cron schedules are not affected by redeployment timing.

Cron Syntax

┌─── minute (0-59)
│ ┌─── hour (0-23)
│ │ ┌─── day of month (1-31)
│ │ │ ┌─── month (1-12)
│ │ │ │ ┌─── day of week (0-7, 0/7=Sunday)
│ │ │ │ │
* * * * *

Expression	Meaning
`0 8 * * *`	Daily at 8 AM UTC
`0 8 * * 1`	Every Monday at 8 AM UTC
`/15 * * *`	Every 15 minutes
`0 0 1 * *`	First day of month at midnight

Deployment

Schedules only activate with modal deploy:

modal deploy --name my-scheduled-app script.py

modal run does NOT activate schedules.

Monitoring

Execution logs: modal-observability (modal app logs <app> --since …)
Use the "run now" button on the App dashboard to trigger manually
Schedules cannot be paused — remove the schedule and redeploy to stop

Go/TypeScript SDK Note

Scheduling (modal.Cron, modal.Period) is Python-only. Go and TypeScript SDKs cannot define schedules.

To trigger Modal Functions on a schedule from Go/TS, use an external scheduler (e.g., cron job, cloud scheduler) that calls fn.Spawn() / fn.spawn().

Symptom Triage

"Schedule doesn't run"

Ensure you used modal deploy, not modal run
Check the schedule parameter syntax
Verify the app is visible in the Modal dashboard

"Cron runs at wrong time"

Default timezone is UTC
Use timezone= parameter: Cron("0 8 * * *", timezone="America/New_York")

"Period resets after deploy"

Expected behavior; Period counts from deployment time
Use Cron for deploy-independent schedules

Reference Map

references/cron-scheduling.md — Cron/Period details, timezone, monitoring

Related Skills

modal-fundamentals — deploy/rollover CLI; schedules require modal deploy
modal-observability — dashboard logs for scheduled runs; .get_dashboard_url()
modal-parallel-execution — fan-out work from a scheduled entrypoint

Guardrails

Schedules only work with modal deploy (not modal run)
Period resets on each redeployment; use Cron for stable schedules
Cannot pause schedules — remove and redeploy to stop
Each scheduled Function runs independently with its own autoscaling

modal-scheduling

Modal Scheduling

When to Use This Skill

Quick Start