If you don't want to continue waiting for Garmin to update their time zone widget to work on the Fenix 5 series, I've released a clone that mostly mimics the original. Full details are in the showcase forum -- https://forums.garmin.com/showthread.php?378815-Widget-Multi-Time-Zone.
Or you can go download it directly from the store -- https://apps.garmin.com/en-CA/apps/b958476c-9dbf-4ba2-b065-a64ca36fef69
Cheers,
Douglas