Ace filmmaker Mani Ratnam's much awaited Tamil romantic-drama "O Kadhal Kanmani" will release worldwide on April 17.The makers shared the release date on Friday.Starring Dulquer Salmaan and Nitya Menon in the lead, the film marks Ratnam's return to the romance genre after a decade.An urban romantic tale, the film is mostly set in Mumbai. The film also marks the reunion of lensman P.C. Sreeram and Ratnam after several years.Double Oscar-winning composer A.R. Rahman has composed tunes for the movie.