Exported Reports (saved in .CSV format) from the Umbrella Dashboard will always display the timestamp in UTC, whereas your Dashboard will display in the timezone set for your user account. The reports themselves are for the time you specified in your user's timezone; the times are simply displayed in their GMT equivalent.
To shift the timezone in the Exported Report to your desired target timezone, you can simply use Microsoft Excel to alter the timezone that is in your exported CSV file.
Given that the targeted cell is in A1 and you need to shift it by -5 hours:
Given that the targeted cell is in B4 and you need to shift it by +2 hours:
You can configure the timezone for your specific user under the Configuration section of the Dashboard.
Our system also reminds you what time zone is being displayed in the "Reports" section.