Click on your account picture and select Profile at the dropdown menu.
Scroll down to the bottom of the page and click on edit in the section Contact, followed by clicking the cell next to Time zone.
This will open a dropdown menu with the available time zones. Either use the search bar at the top of the list or the scroll bar to the side to find your new time zone. Once you locate your new time zone, hover over it and it will turn dark blue. Click on it to select it.
Click the save button in the bottom right to confirm the change.
All entry time stamps and histories will be updated to the new time zone.