Try to add the following code to the theme.js file:
JavaScript
// Add the Estimated Delivery Date event to the Avone theme
shopify.on('product:added', function(product) {
// Get the estimated delivery date
var estimatedDeliveryDate = shopify.orderDeadline.getEstimatedDeliveryDate(product);
// Add the estimated delivery date to the cart line item
var cartLineItem = document.querySelector('[data-product-id="' + product.id + '"]');
cartLineItem.setAttribute('data-estimated-delivery-date', estimatedDeliveryDate);
// Add the estimated delivery date to the order details in admin
var orderDetailsForm = document.querySelector('#order-details-form');
var estimatedDeliveryDateField = orderDetailsForm.querySelector('[name="estimated_delivery_date"]');
estimatedDeliveryDateField.value = estimatedDeliveryDate;
});