Title: Flag of the United States
Content:  50, occurred in 1960 when the present design was chosen, after Hawaii gained statehood in August 1959. Before that, the admission of Alaska in January 1959 prompted the debut of a short-lived 49-star flag. Prior to the adoption of the 48-star flag in 1912, there was no official arrangement of the stars in the canton, although the U.S. Army and U.S. Navy used standardized designs. Throughout the 19th century, there was an abundance of different star patterns, rectangular and circular. On July 4, 2007, the 50-star flag became the version of the flag in the longest use, surpassing the 48-star flag that was used from 1912 to 1959.
Title: 51st state
Content:  If a new U.S. state were to be admitted, it would require a new design of the flag to accommodate an additional star for a 51st state. However, according to the U.S. Army Institute of Heraldry, the United States flag never becomes obsolete. In the event that a new state is added to the Union and a 51-star flag is approved, any approved American flag (such as the 50-star flag) may continue to be used and displayed until no longer serviceable.
Title: Seal of the President of the United States
Content:  Alaska was admitted as the 49th state on January 3, 1959, which caused the 49th star to be added to the United States flag on the following July 4. On May 26, President Eisenhower issued, which added a 49th star to the outer ring on the presidential coat of arms (and therefore the seal and flag as well), also effective on July 4. The order was otherwise identical to Truman's order, which it replaced. Hawaii was admitted as the 50th state on August 21, 1959, and Eisenhower duly issued on February 5, 1960 (effective July 4, 1960) to add the 50th star to the coat of arms. Once again, it was identical to the previous orders other than the number of stars. This remains the official definition today. Because the upcoming admission of Hawaii would cause a further change the following year, no seal dies were made in 1959 with 49 stars, and the 1945 dies continued in use. New dies with 50 stars were made by the Bureau of Engraving and Printing only after the 1960 executive order came into effect.
Title: Flag of the United States
Content:  The current design of the U.S. flag is its 27th; the design of the flag has been modified officially 26 times since 1777. The 48-star flag was in effect for 47 years until the 49-star version became official on July 4, 1959. The 50-star flag was ordered by then president Eisenhower on August 21, 1959, and was adopted in July 1960. It is the longest-used version of the U.S. flag and has been in use for over 61 years.
Title: Five-pointed star
Content:  The five-pointed stars on the flag of the United States were introduced in the Flag Act of 1777. The Flag Act did not specify any particular arrangement, number of points, nor orientation for the stars and the arrangement. Some flag makers arranged the stars into one big star, in a circle or in rows and some replaced a state's star with its initial. One arrangement features 13 five-pointed stars arranged in a circle, with the stars arranged pointing outwards from the circle (as opposed to up), the so-called Betsy Ross flag. The American flag shown in the painting Surrender of Lord 
Title: List of flags of the United States
Content:  Since 1818, a star for each new state has been added to the flag on the Fourth of July the year immediately following each state's admission. In years in which multiple states have been admitted, the corresponding number of stars were added to the flag. This change has typically been the only change made with each revision of the flag since 1777, with the exception of changes in 1795 and 1818, which increased the number of stripes to 15 and then returned it to 13, respectively. As the exact pattern of stars was not specified prior to 1912, many of the historical U.S. national flags (shown below) have had varied arrangements of the stars.
Title: Flag of the President of the United States
Content:  The flag was changed by President Truman in 1945, a process which began with inquiries by President Franklin Roosevelt (who had been involved with the creation of the 1916 flag) shortly before his death. The new flag used the same basic design for the eagle, except (in response to some heraldic criticisms) changed the eagle to face towards its right (dexter, the direction of honor) and thus towards the olive branch, and the eagle was changed to be in full color. Instead of the four stars, a circular ring of 48 stars was added around the eagle. Truman issued on October 25, 1945, which unified the coat of arms, flag, and seal to use the new design. The flag was first flown at the commissioning of the USS Franklin D. Roosevelt (CV-42) two days later. The only changes have been to add more stars for new states; President Eisenhower issued on May 26, 1959 (effective July 4) to add a star for Alaska, and later issued  on February 5, 1960 (again effective the following July 4) to add a 50th star for Hawaii. The design has not changed since.
Title: Timeline of the flag of the United States
Content:  narrowly defeated in the U.S. Senate. The Amendment to the Constitution would make burning the flag a punishable crime. ; 2005 &ndash; U.S. House of Representatives passes a new flag desecration constitutional amendment ; 2006 &ndash; U.S. Senate rejects new constitutional amendment ; 2007 &ndash; The longevity in years used of the present 50-star flag became tied with that of the 48-star flag, both having experienced 47 years of continuous use. After this date, the 50-star flag became the longest-used version of the Flag of the United States of America. The following is a timeline of the flag of the United States.
Title: July 1960
Content: For the first time, a 50-star flag of the United States was hoisted, raised at 12:01 a.m. (EDT), at the Fort McHenry National Monument in Baltimore, and at the U.S. Capitol in Washington. At the time, there were only seven places in the United States where the national flag was permitted to be flown during hours of darkness. 
Title: Flag of the United States
Content:  In 1795, the number of stars and stripes was increased from 13 to 15 (to reflect the entry of Vermont and Kentucky as states of the Union). For a time the flag was not changed when subsequent states were admitted, probably because it was thought that this would cause too much clutter. It was the 15-star, 15-stripe flag that inspired Francis Scott Key to write "Defence of Fort M'Henry", later known as "The Star-Spangled Banner", which is now the American national anthem. The flag is currently on display in the exhibition "The Star-Spangled Banner: The Flag That Inspired the National Anthem" at the Smithsonian Institution National Museum of 

Question: when was the 50th star added to the united states flag?
Answer: 1960.