Amazon has expanded its same-day delivery service in the United States. The web retail giant has added San Francisco, Dallas, and Los Angeles to the list of cities in which the delivery option is available, and has increased the amount of time customers have to order their items in some other regions. The additions mean that Amazon now offers same-day delivery in 12 metropolitan areas. Many other cities in which Amazon same-day delivery was already available have had their deadlines for ordering goods pushed back.