[ML] Update calendar events for anomaly detection jobs fails sometimes

[valeriy42]

Elasticsearch Version

8.17

Installed Plugins

No response

Java Version

bundled

OS Version

Linux

Problem Description

The customer reported that assigning the DST calendar to a job group that contains 1500 anomaly detection jobs failed to enforce the time shift for about 15% of the jobs.

Steps to Reproduce

1. Add all jobs to one group
2. Assign the group to a DST calendar
3. Verify if the model was shifted by 3600 seconds when the DST event occurred.

Logs (if relevant)

No response

[elasticsearchmachine]

Pinging @elastic/ml-core (Team:ML)