To change only your own time zone, click on your name at the top right. In the drop down menu, click on Account & Billing.
Scroll down and change your time zone. This change will only affect your interface.
To set the default time zone of the entire platform, click on Home and change Default Platform Time Zone in the Settings section.
The default platform time zone is the time zone that all users will be set to, unless they a certain time zone specified.
In the event that an admin has a different time zone than a user, the admin's time zone will be converted to the time zone that the user has set. For example, if you have set a course to become available at 8:00 AM PST, any user in the EST time zone would have the course available at 11:00 AM EST.