Event

Timer Start Event

Starts a new process instance when a timer fires. The engine schedules the job when the process definition is deployed and reschedules automatically for cycles.

Properties

Property	Type	Required	Description
ID	string	yes	Unique identifier
Name	string	no	Display label
Timer Type	`duration` \| `date` \| `cycle`	yes	How the timer behaves
Timer Expression	string	yes	ISO 8601 expression (see below)

Timer Expressions

Duration — fire once, after a delay from deployment

Expression	Meaning
`PT30M`	30 minutes
`PT2H`	2 hours
`P1D`	1 day
`P1DT4H30M`	1 day, 4 hours, 30 minutes

Format: P prefix, then [n]Y[n]M[n]D for calendar parts, then T[n]H[n]M[n]S for time parts. Only include units you need.

Date — fire once at an absolute point in time

Expression	Meaning
`2026-06-01T09:00:00Z`	1 Jun 2026 at 09:00 UTC
`2026-06-01T09:00:00+05:30`	1 Jun 2026 at 09:00 IST

Always include a timezone offset or Z (UTC). Omitting it is ambiguous.

Cycle — fire repeatedly, creating a new instance each time

Expression	Meaning
`R/PT1H`	Every hour, forever
`R/P1D`	Every day, forever
`R3/PT30M`	Every 30 minutes, exactly 3 times
`R5/P1DT8H`	Every 1 day 8 hours, 5 times

Format: R[n]/<duration>. Omit n to repeat forever.

XML Example

<!-- Cycle: run daily forever -->
<bpmn:startEvent id="timer_start" name="Daily Batch">
  <bpmn:timerEventDefinition>
    <bpmn:timeCycle>R/P1D</bpmn:timeCycle>
  </bpmn:timerEventDefinition>
  <bpmn:outgoing>flow_to_process</bpmn:outgoing>
</bpmn:startEvent>

<!-- Duration: run once after 1 hour -->
<bpmn:startEvent id="timer_start" name="Delayed Start">
  <bpmn:timerEventDefinition>
    <bpmn:timeDuration>PT1H</bpmn:timeDuration>
  </bpmn:timerEventDefinition>
  <bpmn:outgoing>flow_to_process</bpmn:outgoing>
</bpmn:startEvent>

Notes

Timer start events do not require an API call to trigger — the engine fires them on schedule automatically. To manually start an instance at any time, use a plain Start Event with POST /api/v1/instances.