Custom "product date field" and "overview page" for Woocommerce 3.x

Hi Crowd, I need a - update safe ([login to view URL]) - custom product field (showing a custom date), displayed in the WooCommerce Backend (order details) and (customers order details page). Additionally a overview page/table in the backend with all "order details (order number, order date, completed order date, customer name ect + the new "end of service date" field. Background: We are selling services with a limited timerange (3 and 12 month) from "completed order date" so the end "Date of Service" must be displayed . Example: If i order a 3 months contract, the "end of service date" (completed order date + 3 months (eg 12 Month) must be displayd in the Woocommerce "order details page" and customer "order details page". Maybe a easy way ist to use the "add Meta" function (and field) who is already there in Woocommerce. To trigger time (3 or 12 months) from "complete order date" to "end of service" you can pick up time from product variant. There are 2 variants; 1: "3 Monate" and "12 Monate", so you need to extract "3" or "12" from this fields .. alternative a spinner Button with 3 or 12 months in the Woocommerce Backend product page (NOT frontend)! -------------------------------------------------------------------------> Setting up WordPress and WooCommerce development area is up to you. I await the files & installation/integration instruction because our shop is online/productive.