You may already know that you can add additional time zones (up to 2) when using Outlook.
Well, this option was missing if you were using Outlook Web Access (aka OWA, aka Outlook on the Web).
Good news, you can now do the same when using Outlook Web Access.
Adding additional time zones when using OWA is exactly the same as with Outlook client; connect to your mailbox (https://outlook.office.com/) and access the Settings\View all Outlook settings\Calendar
The Outlook client limit (2 time zones) seems to have been removed; not quite sure now how many different time zone you can add.