The estimated delivery date gives you an indication of how long it will take to receive the item which is based on:
Working days
The estimated delivery is given in carrier working days. Dispatch times don't include Saturdays, Sundays and major holidays. Transit times don't include major holidays and Sundays, but may include Saturdays, depending on the delivery service provider. For example, transit times for Royal Mail services include Monday to Saturday (exception: Royal Mail Special Delivery services include Monday to Friday with an additional charge for Saturday delivery).
Dispatch time
Sellers are required to specify how long they will take to package and post the item after receiving cleared payment. 1 working day.
Delivery services
Some delivery services provide an estimate for the number of working days that it will take to deliver the item to the buyer. This transit time does not include the seller's dispatch time .Delivery company may change depending on item weight.