Here is a list of steps you can take to change the time zone for all events in a specific category of your Microsoft calendar:

1. Launch Microsoft Calendar on your computer.
2. Select the particular category whose time zone you want to change.
3. Click on the File tab in the upper left-hand corner.
4. Find the Options tab in the drop-down list.
5. Choose Advanced in the left-hand column.
6. Locate the Time Zone drop-down menu in the Advanced Options tab.
7. Select the new time zone, and click OK.