Thanks for using Microsoft Q&A forum and posting your query.
Tumbling window triggers in Azure Data Factory are read-only, which means that you cannot edit them directly. If you need to make changes to a tumbling window trigger, you will need to create a new trigger with the desired changes and delete the old trigger.
Feature request: Changing time on tumbling window triggers
Please feel free to up-vote and comment on the above feature request link to help increase the priority of the feature request.
Additional resources: ADF Tumpling Window Trigger Udpating the startTime property behaviour
In case if your requirement can be met using Schedule Triggers, try using schedule triggers if you want to automatically handle time zone offsets.
Hope this info helps.
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