PM Modi surpassed ex-Sikkim CM Pawan Chamling (8,930 days) as India’s longest-serving head of government, combining his Gujarat CM and PM tenures at 8,931 days. Naveen Patnaik ranks next, serving over 8,859 days as Odisha CM. Jyoti Basu is third, serving over 8,329 days as West Bengal CM, while Gegong Apang comes fourth with over 8,250 days as Arunachal CM.