Oldest trains still running

Trains keep getting their schedules changed, their routes changed, and their names changed over time, so the answers to these questions are a bit fluid. The Bangalore Mail has been running in various guises since 1864 (1862?). The Deccan Queen and the Howrah-Madras Mail have been in operation since the 1930s. So has the Howrah-Kalka Mail. The Punjab Mail, the Frontier Mail, and the Grand Trunk Express are other trains that have been running for a long time, however, their names have changed and/or their routes / termini have changed too. The 2 Up / 1 Dn Mail between Calcutta and Delhi, started in 1866, is the direct forebear of today's Howrah-Kalka Mail. The Poona Mail (Bombay-Poona) introduced in the 1860s was discontinued in the 1970s. The Flying Ranee started under that name in 1950, but it had its predecessors (Flying Queen, Weekend Special) in 1937 and 1906.