Daylight Saving Time Effects on DataWorks Scheduled Tasks - DataWorks

When daylight saving time (DST) begins or ends, the number of task instances generated and their scheduled times may change. This topic explains how DataWorks handles both transitions so you can anticipate and plan for the effects.

Limitations

Only tasks in regions that observe DST are affected.

How it works

DataWorks scheduling is clock-based, not interval-based. Tasks run at their designated clock times, not at fixed elapsed intervals. This distinction drives all DST behavior:

Tasks scheduled by hour or minute: The total number of daily instances changes on transition days, because the day itself has 23 or 25 hours.
Tasks scheduled by day, week, or month: Only tasks whose scheduled time falls within the skipped or repeated hour are affected. Tasks outside that window run normally.

The examples in this topic use a UTC-8 time zone region where DST begins at 02:00 (clocks spring forward to 03:00).

To avoid DST-related scheduling changes entirely, configure your workspace to use a time zone that does not observe DST, such as UTC.

When DST begins

Clocks spring forward from 02:00 to 03:00, so the transition day has only 23 hours.

Impact on instance generation

Tasks scheduled by hour or minute

On the transition day, no instance is generated for the 02:00 slot — that hour does not exist. A task scheduled to run every hour generates 23 instances instead of the usual 24.

A time offset also occurs: the scheduling time of some instances shifts one hour forward. For example, the instance generated in the fourth scheduling cycle for an hourly task is normally scheduled at 04:00, but on the day when DST begins, its scheduling time changes to 05:00.

Tasks scheduled by day, week, or month

An instance is still generated on the transition day. Whether it runs depends on the task's scheduled time:

If the scheduled time falls between 02:00 and 03:00, DataWorks delays execution by one hour and generates a dry-run instance instead.
If the scheduled time falls outside the 02:00–03:00 range, the instance runs normally.

Ten minutes before 03:00 is 01:50, not 02:50.

Impact on scheduling parameter values

Scheduling parameters calculated from the scheduled time are also affected.

Scenario	Scheduled time	Parameter format	Normal value	Value when DST begins
1	`03:00`	`$[hh24-1/24]`	`02:00`	`01:00`
2	`02:00`	`$[hh24-1/24]`	`01:00`	`01:00`

In Scenario 2, the parameter value does not change. However, if the task is scheduled by day, DataWorks generates a dry-run instance on the transition day.

When DST ends

The transition day has 25 hours, with 02:00 occurring twice.

Impact on instance generation

Tasks scheduled by hour or minute

The day has 25 hours, but DataWorks still generates 24 instances for a task scheduled by hour. Two instances share the scheduled time 02:00. Only the second instance at 02:00 is retained; the first is discarded.

Ten minutes before 02:00 is 02:50, not 01:50.

Impact on scheduling parameter values

Because 02:00 appears twice, scheduling parameters calculated from the scheduled time may shift.

Scenario	Scheduled time	Parameter format	Normal value	Value when DST ends
1	`03:00`	`$[hh24-2/24]`	`01:00`	`02:00`
2	`02:00`	`$[hh24-1/24]`	`01:00`	`02:00`