Hey Sean,
Sorry for the delayed response here! It is unfortunately not possible to add timezones there. 🙁
Well, it is technically possible, but would take a large amount of custom coding and delicate implementation of custom timezones.
Our plugins use the timezones provided by PHP and WordPress itself. If you head to Settings → General in your wp-admin, you’ll notice that the timezone options there are the same ones that end up in the various timezone pickers in our plugins. The “colloquial” / common named timeones like “EST”, “Central”, “Mountain” etc. are unfortunately not available at this time.
I hate to bear that news! Please let me know if there’s anything else I can try to help with.
Sincerely,
George