I do not know all time zone abbreviations, but I can handle numbers :)
@ -524,6 +524,7 @@
(use-package calender
:init (setq calendar-date-style 'iso
calendar-time-zone-style 'numeric
calendar-week-start-day 1 ; Monday
calendar-bahai-all-holidays-flag nil
calendar-chinese-all-holidays-flag nil