Hi Nebo,
The field you are looking for is called CreatedDate.
You might be asking why is there a difference?
The reason why the field name is slightly different is because the Lead List screen is based off of the Contact table and the New / Edit Lead Screen is based on the Customer table.
The EntityCreatedDate field in the Contact table is a linked field from the CreatedDate field in the Entity table.
Linked fields are fields which have a relationship with another table using a common identifier; in this case, it is the customer name.
Hope this helps,
Nelson