Hello @Vallespi, Xavi ,As per Microsoft Documentation https://learn.microsoft.com/en-us/graph/api/resources/plannerplan?view=graph-rest-1.0, we can't get lastModifiedTime of a planner task using Graph API call.
You can reliably use the ETag to detect if the data in the backend is different (for each entity, task and task details are different entities), if you store the ETag on the backend instead of the last modified date. Please check https://stackoverflow.com/questions/71644435/how-to-get-the-last-modified-date-and-time-of-a-microsoft-planner-task-using-mic.
We encourage you to submit your feedback on this issue to our feedback portal: https://aka.ms/graphfeedback This portal is monitored by our product team, and they will consider your feedback for future improvements.
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