When daylight saving time (DST) starts or ends, nodes in DST-observing regions behave differently from a normal day. This topic explains how DST transitions affect instance generation and scheduling parameter values for nodes scheduled by hour, day, week, or month.
Only nodes in regions where DST is observed are affected.
How DST affects scheduling
DataWorks schedules nodes based on wall-clock time. When the clock jumps forward or back, the skipped or repeated hour directly affects how many instances are generated and what values scheduling parameters resolve to.
The behavior depends on the node's scheduling frequency:
| Scheduling frequency | DST starts (clock moves forward) | DST ends (clock moves back) |
|---|---|---|
| By hour or minute | 23 instances generated; no instance at 02:00 |
24 instances generated; only the second 02:00 instance is retained |
| By day, week, or month | Instance may be skipped (dry-run) if scheduled within the skipped time window | — |
Limitations
Only nodes in regions where DST is observed are affected when DST starts or ends.
When DST starts
When DST starts, the clock moves forward from 02:00 to 03:00. The one-hour window from 02:00 to 03:00 does not exist on that day.
Impact on instance generation
Nodes scheduled by hour or minute
On a normal day, an hourly node generates 24 instances. On the day DST starts, only 23 instances are generated — no instance is created for the 02:00 slot because that time does not exist.
The following figure shows the scheduling cycle settings for an hourly auto triggered node:
Nodes scheduled by day
Whether the instance runs normally depends on the node's scheduling time:
-
If the scheduling time falls within
02:00–03:00(the skipped window): DataWorks delays the scheduling time by one hour and generates a dry-run instance for the node. -
If the scheduling time falls outside
02:00–03:00: the instance runs normally.
The following figure shows the scheduling cycle settings for a daily node:
Nodes scheduled by week or month follow the same rule as daily nodes. If the scheduled time falls in the skipped window, DataWorks generates a dry-run instance. Ten minutes before 03:00 is 01:50.
Impact on scheduling time offset
For hourly nodes, the scheduling time of some instances shifts forward by one hour. For example, the instance in the 4th scheduling cycle normally has a scheduling time of 04:00. On the day DST starts, its scheduling time changes to 05:00.
Impact on scheduling parameter values
Scheduling parameters whose values are calculated from the scheduling time are affected when the clock moves forward.
| Scenario | Scheduling time | Parameter format | Normal value | Value on DST start |
|---|---|---|---|---|
| 1 | 03:00 |
$[hh24-1/24] |
02:00 |
01:00 |
| 2 | 02:00 |
$[hh24-1/24] |
01:00 |
01:00 (no change; daily nodes generate a dry-run instance) |
When DST ends
When DST ends, the clock moves back from 03:00 to 02:00. The day has 25 hours, with 02:00 occurring twice.
Impact on instance generation
For hourly nodes, 24 instances are generated — the same as a normal day. Two instances share the scheduling time 02:00. Only the second 02:00 instance is retained; the first is discarded.
Ten minutes before 02:00 is 02:50.
Impact on scheduling parameter values
Because the day includes two 02:00 slots, scheduling parameter values calculated from the scheduling time may differ from normal days.
| Scenario | Scheduling time | Parameter format | Normal value | Value on DST end |
|---|---|---|---|---|
| 1 | 03:00 |
$[hh24-2/24] |
01:00 |
02:00 |
| 2 | 02:00 |
$[hh24-1/24] |
01:00 |
02:00 |