Cron Expression Tester
A practical reference for teams that need to validate when a cron schedule will actually run.
Cron Expression Tester from Sandglass helps you validate when a cron schedule will actually run. Use the result to decide what to monitor continuously.
When to reach for this tool
Reach for this when you need to validate when a cron schedule will actually run during setup, debugging, or an incident review. A one-off check is useful for diagnosis, but production systems need continuous monitoring once the immediate question is answered.
- Check the next several run times, not just the next one.
- Time zone and daylight-saving shifts change when a job fires.
- The expected interval drives the heartbeat grace period.
From one-off check to continuous monitor
Use the tester to confirm the next expected run times, then set a heartbeat interval with a realistic grace period so normal scheduling jitter does not raise false alarms.
- Recreate the same check in Sandglass on an interval so the next change is caught without re-running the lookup.
- Send failures to email, a Slack webhook channel, or a generic webhook owned by whoever fixes the problem.
- Track the result over time instead of treating one manual reading as the final answer.
Why a lookup is not monitoring
A schedule that looks right can still surprise you across time zones and daylight-saving changes. Verify the concrete next run times rather than trusting the expression at a glance.
Use this tool well
Step 1: Run the check and read the result
Use the output to confirm the current state, and treat anything surprising as a starting point for diagnosis rather than a verdict.
Step 2: Define what healthy means
Write down which results count as healthy, degraded, or failed before you automate anything.
Step 3: Promote it to a continuous monitor
Recreate the same check in Sandglass on an interval so the next change is caught automatically.
Step 4: Route the alert to an owner
Send failures to email, a Slack webhook channel, or a generic webhook owned by whoever will fix them.