I am trying to create a report which provides a breakdown by the assignee of the number of tickets open or closed within the past 30 days.
You would like to use some calculated member to retrieve the last 30 days in Time dimension. You can check out our demo account:
Some of the reports there have Time dimension with several calculated members representing different periods. Please check any report. You can open any report and check more calculated member examples for time dimension.
You can easily export and import those reports into your accounts. You can open any other calculated member formula from this account as well.
Martins / eazyBI support