New Delhi, Jan 14: Prime Minister Narendra Modi on Saturday extended greetings to people of various communities as they celebrate harvest festivals, and said diversity is India's greatest strength.Modi in a series of tweets greeted people on the occasion of Makar Sankranti, Pongal, Magh Bihu and Uttarayan."Today (January 14) people across India are celebrating various festivals. My greetings to everyone celebrating these auspicious festivals," Modi tweeted."May these festivals bring abundance of happiness and prosperity in the lives of our hardworking farmers," Modi said."These and many other festivals celebrated across India that add great colour and happiness in our lives. This diversity is India's greatest strength."Modi also greeted people on the occasion of Makar Sankranti and wished that this day bring joy and prosperity in everyone's lives.He wished Tamil people a happy and blessed Pongal, greeted Gujaratis for Uttarayan and people of Assam on the occasion of Magh Bihu.