Makar Sankranti which follows the Gregorian calendar, falls on 14th of January every year. On some occasions it falls on 15th because of the revolution of earth. Unlike other Indian festivals which follow Lunar calendar, this festival follows solar calendar.
Why is it called Makar Sankranti?
The sun enters the sun-sign of Capricon or Makar Rashi (as it is called in India) on this day. Thus the name Makar. Sankranti is movement of sun from one rashi to another. Celebrated with utmost zeal, this festival brings out the tradition of celebrating celestial forces.