From the 17th century onwards, interest in the old library, with its manuscripts and incunabulae, went into decline and the modern library in the Jesuit College came to the fore. In 1756, the oldest university library was finally closed down and its books, 2,787 volumes, were incorporated into the Court Library, of which Gerard van Swieten was then director. After the dissolution of the Jesuit order (1773), the new "Academic Library" was created out of the book collections of the five Lower Austrian Colleges and a large number of duplicates from the Court Library. This was opened on 13 May 1777, the birthday of Maria Theresa of Austria, in the building of the Academic College. Initially, the stock consisted of some 45,000 books and during Emperor Joseph IIs dissolution of the monasteries, this was soon considerably extended. In contrast to its antecedents, the new library was open to the general public. Between 1827 and 1829, it acquired the classicist extension (Postgasse 9) to the Academic College, in which it was to be accommodated until 1884. In this year, the main library, with some 300,000 books, moved to Heinrich von Ferstels new Main Building on the Ring, where stacks for some 500,000 volumes had already been prepared. With an annual growth of up to 30,000 volumes, the surplus space was soon filled. Book storage space had to be extended continuously. One hundred years later, the complete library, including departmental and subject libraries, comprised more than 4.3 million volumes. Today, Viennas University Library is the largest collection of books in Austria, still facing problems of space. In addition to the Main Library, which alone has to cope with an annual growth of 40,000 volumes, it includes three Faculty Libraries, 32 Subject Libraries and 26 Departmental Libraries.
Question: Over how many years did id acquire the classicist extension?
Answer: 2; 2