when does us postal service deliver packages typically depends on the type of service used and the destination. For most domestic packages, USPS delivers Monday through Saturday. Delivery times for regular mail are typically between 9 a.m. and 5 p.m., with extended hours for some packages, such as Priority Mail Express, which may be delivered later in the evening. Some services, like Priority Mail and Priority Mail Express, offer guaranteed delivery times, while others, like First-Class Mail, may vary. For international shipments, delivery times depend on the destination country.