Question: When did Chopin return to the city where Esperanto was created?

full_context: Document 1: Dialect: In the early 20th century, the vast conscription of Italian men from all throughout Italy during World War I is credited with facilitating the diffusion of standard Italian among less educated Italian men, as these men from various regions with various regional languages were forced to communicate with each other in a common tongue while serving in the Italian military. With the eventual spread of the radio and television throughout Italy and the establishment of public education, Italians from all regions were increasingly exposed to standard Italian, while literacy rates among all social classes improved. Today, the majority of Italians are able to speak standard Italian, though many Italians still speak their regional language regularly or as their primary day-to-day language, especially at home with family or when communicating with Italians from the same town or region. However, to some Italians, speaking a regional language, especially in a formal setting or outside of one's region, may carry a stigma or negative connotations associated with being lower class, uneducated, boorish, or overly informal.
Document 2: Kazimierz Bein: He was also, for a time, a prominent Esperanto author, translator and activist, until in 1911 he suddenly, without explanation, abandoned the Esperanto movement. Bein became at least as well known for his involvement with Esperanto as for his medical accomplishments, and as much for the manner in which he left the Esperanto movement as for what he had accomplished within it.
Document 3: Frédéric Chopin: Back in Warsaw that year, Chopin heard Niccolò Paganini play the violin, and composed a set of variations, Souvenir de Paganini. It may have been this experience which encouraged him to commence writing his first Études, (1829–32), exploring the capacities of his own instrument. On 11 August, three weeks after completing his studies at the Warsaw Conservatory, he made his debut in Vienna. He gave two piano concerts and received many favourable reviews—in addition to some commenting (in Chopin's own words) that he was "too delicate for those accustomed to the piano-bashing of local artists". In one of these concerts, he premiered his Variations on Là ci darem la mano, Op. 2 (variations on an aria from Mozart's opera Don Giovanni) for piano and orchestra. He returned to Warsaw in September 1829, where he premiered his Piano Concerto No. 2 in F minor, Op. 21 on 17 March 1830.
Document 4: Frédéric Chopin: Although it is not known exactly when Chopin first met Liszt after arriving in Paris, on 12 December 1831 he mentioned in a letter to his friend Woyciechowski that "I have met Rossini, Cherubini, Baillot, etc.—also Kalkbrenner. You would not believe how curious I was about Herz, Liszt, Hiller, etc." Liszt was in attendance at Chopin's Parisian debut on 26 February 1832 at the Salle Pleyel, which led him to remark: "The most vigorous applause seemed not to suffice to our enthusiasm in the presence of this talented musician, who revealed a new phase of poetic sentiment combined with such happy innovation in the form of his art."
Document 5: Jerzy Żuławski: In a twenty-year writing career, from his first book of poems in 1895, at the age of 21, to his final World War I dispatches in 1915, Jerzy Żuławski created an impressive body of work—seven volumes of poetry, three collections of literary criticism, numerous cultural and philosophical essays, ten plays and five novels. He was considered an important and influential intellectual figure in the early years of the 20th century, but a century later, the only creation which has remained in print and assured him literary immortality is "The Lunar Trilogy". Stanisław Lem (1921–2006), renowned as the "most widely read science-fiction writer in the world", contributed an introduction to the 1956 and 1975 editions of the "Trilogy"'s initial volume, "Na Srebrnym Globie" ("On the Silver Globe"), crediting Żuławski's words with inspiring him to become "a writer of the fantastic" and describing the time he spent reading "The Lunar Trilogy" as "one of the most fascinating and life-changing experiences" of his youth.
Document 6: Esperanto: Esperanto was created in the late 1870s and early 1880s by L. L. Zamenhof, a Polish-Jewish ophthalmologist from Białystok, then part of the Russian Empire but now part of Poland. According to Zamenhof, he created the language to reduce the "time and labour we spend in learning foreign tongues" and to foster harmony between people from different countries: "Were there but an international language, all translations would be made into it alone ... and all nations would be united in a common brotherhood." His feelings and the situation in Białystok may be gleaned from an extract from his letter to Nikolai Borovko:
Document 7: Boris Kolker: Dr. Kolker learned Esperanto in 1957 and is the author of articles on interlinguistics, book reviews and three famous Esperanto textbooks for students of different levels. Due to the great popularity of his book eo:Vojaĝo en Esperanto-lando (Travels in Esperanto-Land), which is both a proficiency course in Esperanto and a guidebook to Esperanto culture, he is known to many as a guide to Esperanto-Land.Kolker is a member of the Academy of Esperanto, an honorary member of the World Esperanto Association (Universala Esperanto Asocio), and an associate editor of the monthly magazine Monato. For two decades he headed a large-scale Esperanto correspondence course in Russia that graduated around 900 students. He also taught Esperanto at American universities in San Francisco and Hartford.
Document 8: Kontakto: Kontakto is an Esperanto magazine published by TEJO and supported by the Universal Esperanto Association (UEA). The magazine has readers in about 90 countries of the world. It started in 1963 through a proposal of the UEA committee by Humphrey Tonkin, who became its first editor in chief and who provided a magazine that touched on topics of interest to Esperanto youth. The magazine often used the slogan "In Esperanto, but not about Esperanto."
Document 9: Frédéric Chopin: Chopin took the new salon genre of the nocturne, invented by the Irish composer John Field, to a deeper level of sophistication. He was the first to write ballades and scherzi as individual concert pieces. He essentially established a new genre with his own set of free-standing preludes (Op. 28, published 1839). He exploited the poetic potential of the concept of the concert étude, already being developed in the 1820s and 1830s by Liszt, Clementi and Moscheles, in his two sets of studies (Op. 10 published in 1833, Op. 25 in 1837).
Document 10: Esperanto: After some ten years of development, which Zamenhof spent translating literature into Esperanto as well as writing original prose and verse, the first book of Esperanto grammar was published in Warsaw on July 26, 1887. The number of speakers grew rapidly over the next few decades, at first primarily in the Russian Empire and Central Europe, then in other parts of Europe, the Americas, China, and Japan. In the early years, speakers of Esperanto kept in contact primarily through correspondence and periodicals, but in 1905 the first World Congress of Esperanto speakers was held in Boulogne-sur-Mer, France. Since then world congresses have been held in different countries every year, except during the two World Wars. Since the Second World War, they have been attended by an average of more than 2000 people and up to 6000 people.
Document 11: Frédéric Chopin: Four boarders at his parents' apartments became Chopin's intimates: Tytus Woyciechowski, Jan Nepomucen Białobłocki, Jan Matuszyński and Julian Fontana; the latter two would become part of his Paris milieu. He was friendly with members of Warsaw's young artistic and intellectual world, including Fontana, Józef Bohdan Zaleski and Stefan Witwicki. He was also attracted to the singing student Konstancja Gładkowska. In letters to Woyciechowski, he indicated which of his works, and even which of their passages, were influenced by his fascination with her; his letter of 15 May 1830 revealed that the slow movement (Larghetto) of his Piano Concerto No. 1 (in E minor) was secretly dedicated to her – "It should be like dreaming in beautiful springtime – by moonlight." His final Conservatory report (July 1829) read: "Chopin F., third-year student, exceptional talent, musical genius."
Document 12: Frédéric Chopin: Possibly the first venture into fictional treatments of Chopin's life was a fanciful operatic version of some of its events. Chopin was written by Giacomo Orefice and produced in Milan in 1901. All the music is derived from that of Chopin.
Document 13: Frédéric Chopin: From September 1823 to 1826 Chopin attended the Warsaw Lyceum, where he received organ lessons from the Czech musician Wilhelm Würfel during his first year. In the autumn of 1826 he began a three-year course under the Silesian composer Józef Elsner at the Warsaw Conservatory, studying music theory, figured bass and composition.[n 3] Throughout this period he continued to compose and to give recitals in concerts and salons in Warsaw. He was engaged by the inventors of a mechanical organ, the "eolomelodicon", and on this instrument in May 1825 he performed his own improvisation and part of a concerto by Moscheles. The success of this concert led to an invitation to give a similar recital on the instrument before Tsar Alexander I, who was visiting Warsaw; the Tsar presented him with a diamond ring. At a subsequent eolomelodicon concert on 10 June 1825, Chopin performed his Rondo Op. 1. This was the first of his works to be commercially published and earned him his first mention in the foreign press, when the Leipzig Allgemeine Musikalische Zeitung praised his "wealth of musical ideas".
Document 14: Frédéric Chopin: At the end of 1831, Chopin received the first major endorsement from an outstanding contemporary when Robert Schumann, reviewing the Op. 2 Variations in the Allgemeine musikalische Zeitung (his first published article on music), declared: "Hats off, gentlemen! A genius." On 26 February 1832 Chopin gave a debut Paris concert at the Salle Pleyel which drew universal admiration. The critic François-Joseph Fétis wrote in the Revue et gazette musicale: "Here is a young man who ... taking no model, has found, if not a complete renewal of piano music, ... an abundance of original ideas of a kind to be found nowhere else ..." After this concert, Chopin realized that his essentially intimate keyboard technique was not optimal for large concert spaces. Later that year he was introduced to the wealthy Rothschild banking family, whose patronage also opened doors for him to other private salons (social gatherings of the aristocracy and artistic and literary elite). By the end of 1832 Chopin had established himself among the Parisian musical elite, and had earned the respect of his peers such as Hiller, Liszt, and Berlioz. He no longer depended financially upon his father, and in the winter of 1832 he began earning a handsome income from publishing his works and teaching piano to affluent students from all over Europe. This freed him from the strains of public concert-giving, which he disliked.
Document 15: Estonian language: From 1525 to 1917 14,503 titles were published in Estonian, as opposed to the 23,868 titles which were published between 1918 and 1940.[citation needed]
ground_truth: September 1829
sub_queries: What city was Esperanto formed in? Answer: Warsaw
When did Chopin return to Warsaw ? Answer: September 1829