Prime Minister Narendra Modi has become the longest serving PM of non-Congress political stock, surpassing the 2,268 days that his BJP senior Atal Bihari Vajpayee had clocked in his three terms combined.Prime Minister Narendra Modi has become the longest serving PM of non-Congress political stock, surpassing the 2,268 days that his BJP senior Atal Bihari Vajpayee had clocked in his three terms combined.