To set the user time zone, either go to Users (left menu) → Select user → Edit user (gear icon on top) → Timezone.
Or click on your profile picture (bottom left corner) → My Settings → Regional & Language Settings → Time zone to set your own one.
NOTE: The user time zone needs to be the same as the computer time zone in order for the tracked time entries to be displayed correctly.
NOTE: If you’re a project manager or admin, you will see other people’s time entries converted to your own time zone (in case your time zone is different from theirs).