App locale changes the date and time format based on the locale as well as the date and time labels into the language of the locale. Please note - this does not fully translate the rest of the labels in the app. Your default locale is selected based on your browser geo-location.
App timezone sets the timezone of your app so that the schedule dynamically scrolls on your users' devices to upcoming events in that schedule. You should set the timezone of your app to the timezone your events are in. Please note that time will not dynamically change to your current time zone. For example if you have an event in your schedule at 12pm ET, if you open the app in California at 8:59 am PT it will still show the 12pm ET event as next up at 12pm.
To change the locale and/or timezone of your app, go to the settings section of your app from the Editor. You will land on app settings. Change the settings to your desired locale and/or timezone. You will need to go back to the Editor to publish your app for the changes to take effect.