Question: Which opera was written earlier, Rienzi or Amahl and the Night Visitors? 

Context articles: Martin's Lie
Amahl and the Night Visitors (film)
Chet Allen (actor, born 1939)
Labyrinth (opera)
Amahl and the Night Visitors
Help, Help, the Globolinks!
Rienzi
List of Christmas operas
Rosemary Kuhlmann
Gian Carlo Menotti

Martin's Lie is a chamber opera in one act with music and an English language libretto by Gian Carlo Menotti.
 Commissioned by CBS, it was Menotti's third opera for television after "Amahl and the Night Visitors" and "Labyrinth".
 Although not initially conceived as a work for the stage, the opera premiered in a live theatrical performance on 3 June 1964 at the Bristol Cathedral for the opening of the 17th annual Bath International Music Festival.
 The opera was subsequently filmed with the same cast for television under the direction of Kirk Browning.
 The production used sets and costumes by designer Anthony Powell, and was broadcast nationally by CBS for the opera's United States premiere on 30 May 1965.
Amahl and the Night Visitors is a 1957 Australian TV play.
 It was a filmed version of the opera "Amahl and the Night Visitors" by Menotti.
 The ABC had previously televised Menotti's "The Telephone" and this was the second opera they broadcast.
Chet R. Allen (May 6, 1939 – June 17, 1984) was an American child actor of the 1950s known for his role as Amahl in Gian Carlo Menotti's "Amahl and the Night Visitors", the first opera written for television, which he made with the NBC Opera Theatre.
Labyrinth is an opera in one act by composer Gian Carlo Menotti.
 The work was commissioned for television by the NBC Opera Theatre and uses an English language libretto by the composer.
 Unlike Menotti's previous television operas, such as "Amahl and the Night Visitors", this opera was written with no intention of being moved to live stage performance later.
 Menotti intended for this work to utilize the special effects unique to television which could not be recreated in live theatre.
 As a result, NBC's television production of the opera is the only performance the work has received.
 At its premiere in March 1963 the opera was mainly criticized by the press for its trite use of allegory and music which rejected the avante garde in favour of romanticism.
 Critic Harold C. Schonberg stated in his review in "The New York Times" that, "Menotti falls back on the procedures he has always used: the scraps of canonic imitation, the stretches of parlando, the Puccini like melodies, the banal waltz themes... [It] ended up an allegory that had all the dimension of a Mobius strip: an example of slick television and cinema of the 1960s wedded pretty much to music of the 1890s... On the whole "Labyrinth" is one of the thinnest musical concoctions Menotti has ever put together.
Amahl and the Night Visitors is an opera in one act by Gian Carlo Menotti with an original English libretto by the composer.
 It was commissioned by NBC and first performed by the NBC Opera Theatre on December 24, 1951, in New York City at NBC studio 8H in Rockefeller Center, where it was broadcast live on television from that venue as the debut production of the "Hallmark Hall of Fame".
 It was the first opera specifically composed for television in America.
Help, Help, the Globolinks!
 is an opera in four scenes by Gian Carlo Menotti with an original English libretto by the composer.
 It was commissioned by the Hamburg State Opera and first performed as "Hilfe, Hilfe, die Globolinks!"
 in a German translation by on December 21, 1968 in a double bill with Menotti's "Amahl and the Night Visitors".
 The opera had its English language premiere on August 1, 1969 in the United States at the Santa Fe Opera in a double bill with Igor Stravinsky's "The Nightingale".
 Both premiere productions were directed by the composer.
 Many of the cast members from the Santa Fe production reprised their roles for the work's New York debut at the New York City Opera in December 1969.
Rienzi, der Letzte der Tribunen ("Rienzi, the Last of the Tribunes"; WWV 49) is an early opera by Richard Wagner in five acts, with the libretto written by the composer after Edward Bulwer-Lytton's novel of the same name (1835).
 The title is commonly shortened to Rienzi.
 Written between July 1838 and November 1840, it was first performed at the Hofoper, Dresden, on 20 October 1842, and was the composer's first success.
Christmas operas are operas which are thematically based on either the Nativity of Jesus or secular Christmas stories.
 The earliest Christmas operas appeared in the early 17th century, not long after the creation of the art form.
 Because of the ban on secular theatrical works during the season of Advent, these early Christmas operas, while elaborately staged, were based on religious themes relating to the Nativity.
 By the mid 19th century the ban on secular operas during Advent had ceased, and operas based on a wider array of Christmas themes, such as Santa Claus and King Wenceslaus, emerged.
 Several operas have been inspired by Charles Dickens' "A Christmas Carol", including works by composers Bernard Herrmann and Thea Musgrave.
 The story of the Magi has also been the basis of several operas, including Gian Carlo Menotti's 1951 opera "Amahl and the Night Visitors".
 Initially written for television performance, Menotti's opera has become the only modern Christmas opera to earn an enduring place in the live opera performance repertoire.
 In the 21st century, composer Kevin Puts' "Silent Night" (2011) achieved critical success and won the Pulitzer Prize for music in 2012.
Rosemary Kuhlmann (born January 30, 1922) is an American operatic mezzo-soprano and Broadway musical actress most known for originating the role of the Mother in Gian Carlo Menotti's "Amahl and the Night Visitors", the first opera commissioned for television.
 Kuhlmann portrayed the role on the annual live NBC broadcast of the production from 1951 through 1962.
Gian Carlo Menotti (] ; July 7, 1911 – February 1, 2007) was an Italian-American composer and librettist.
 Although he often referred to himself as an American composer, he kept his Italian citizenship.
 He wrote the classic Christmas opera "Amahl and the Night Visitors", along with over two dozen other operas intended to appeal to popular taste.