1925: That's when Brahmaputra Mail use to start and connect GHY-Tibsukia & kept running past independence (even after HWH-GHY Assam Mail link was broken)..the same schedule was kept as GHY-Tinsukia MG connection to link DLI-GHY BG!!
But all these info holds no stand at IRI & hence i am out of these historical trivia!!