The correct use of the Time Zone feature is of the utmost importance for computer forensics because it might reflect the wrong MAC time of files contained in the evidence, making a professional use the wrong information in an investigation report.
Based on this, you must configure the time zone to reflect the location where the evidence was acquired. For example, if you conducted the acquisition of a computer that was located in Los Angeles, US, and bring the evidence to Sao Paulo, Brazil, where your lab is situated, you should adjust the time zone to Los Angeles so that the MAC time of files can reflect the actual moment of its modification, alteration, or creation.
The FTK allows you to make that time zone change at the same time that you add a new evidence to the case. Select the time zone of the evidence where it was seized from the drop-down list in the Time Zone field. This is required to add evidence in the case.
Take a look at the following screenshot: