Microsoft Exam AZ-305 Topic 4 Question 7 Discussion

Activity logs are kept for 90 days. You can query for any range of dates, as long as the starting date isn't more than 90 days in the past.

Through activity logs, you can determine:

what operations were taken on the resources in your subscription

who started the operation

when the operation occurred

the status of the operation

the values of other properties that might help you research the operation

https://docs.microsoft.com/en-us/azure/azure-resource-manager/management/view-activity-logs

https://docs.microsoft.com/en-us/azure/automation/change-tracking