This is a premium feature and requires the Standard plan or above.
You can customize the delivery time shown to your customers based on their selected country / market.
Market specific delivery times are based off of Shopify Markets, not your customer's actual location. You can only set custom delivery times for markets that you're selling in.
If you are using multiple markets you will need auto-direction enabled. You can follow the Shopify guide here.
From the Arrives By app go to the Markets section. Here you can see all the available markets on your store and any custom delivery times they have.
Markets are based on your store's active markets in Shopify
Select the a market to edit its delivery settings. Note that you must set the status to "Active" to make it live on your store. If the market is not active then default delivery times (including custom rules) are displayed for customers shopping in this market.
You can configure default behavior for the market including business days.
Custom rules for markets
You can further customize markets by adding additional custom rules.
This lets you do things like set different delivery times for specific products (or collections, vendor, etc) in different markets.