Question: When did phone numbers change to 7 digits?

Disambiguated questions and answers:
context: The new numbering plan was officially accepted in October 1947, dividing most of North America into eighty-six numbering plan areas (NPAs). Each NPA was assigned a numbering plan area code, often abbreviated as "area code". These codes were first used by long-distance operators to establish long-distance calls between toll offices. The first customer-dialed direct call using area codes was made on November 10, 1951, from Englewood, New Jersey, to Alameda, California. Direct distance dialing (DDD) was subsequently introduced across the country. By the early 1960s, most areas of the Bell System had been converted and DDD had become commonplace in cities and most larger towns.
question: When did North American plan to change all phone numbers to 7 digits get accepted?
short_answers: October 1947
wikipage: North American Numbering Plan
context: The new network design, completed in 1947, provided for 152 area codes, each with a capacity to serve 540 central offices. Originally only 86 area codes were assigned. New Jersey received the first area code in the new system, area code 201. The second area code, 202, was assigned to the District of Columbia. The allocation of area codes was readjusted as early as 1948 to account for inadequacies in some metropolitan areas. For example, the Indiana numbering plan area 317 was divided to provide a larger numbering pool in the Indiana suburbs of Chicago (area code 219).
question: When was the first new area code received by a locale, an indication of when North American phone numbers changed to 7 digits?
short_answers: 1947
wikipage: North American Numbering Plan
context: The new numbering plan was officially accepted in October 1947, dividing most of North America into eighty-six numbering plan areas (NPAs). Each NPA was assigned a numbering plan area code, often abbreviated as "area code". These codes were first used by long-distance operators to establish long-distance calls between toll offices. The first customer-dialed direct call using area codes was made on November 10, 1951, from Englewood, New Jersey, to Alameda, California. Direct distance dialing (DDD) was subsequently introduced across the country. By the early 1960s, most areas of the Bell System had been converted and DDD had become commonplace in cities and most larger towns.
question: When was the first customer call using the NANP made, an indication of when North American phone numbers changed to 7 digits?
short_answers: November 10, 1951
wikipage: North American Numbering Plan

Long-form answers:
knowledge: content: When making a local call or a call within their numbering plan area, the area code was omitted, resulting in seven-digit dialing.
wikipage: North American Numbering Plan
content: Ten-digit dialing was only necessary when placing foreign area calls to subscribers in another state or numbering plan area.
wikipage: North American Numbering Plan
long_answer: North America adopted a new phone numbering plan in October 1947. The new system limited phone numbers to seven digits, but could include a three digit area code if the call was not local. Area codes were determined by dividing most of North America into eighty-six numbering plan areas (NPAs). This new system was initially only used by long-distance telephone operators until November 10, 1951, when the first customer-dialed direct call using area codes was made from Englewood, New Jersey, to Alameda, California.