Makar means Capricorn and Sankranti is transition. There is a sankranti every month when the sun passes from one sign of the zodiac to the next. There are twelve signs of the zodiac, and thus there are twelve sankranti’s as well. Each of these sankranti’s has its own relative importance but two of these are more important – the Mesh (Aries) Sankranti and the most important, the Makar (Capricorn) Sankranti.
Transition of the Sun from Sagittarius to Capricorn, during the winter solstice in the northern hemisphere is known as Makar Sankranti. From this day begins the six-month long Uttarayana, considered very auspicious for attaining higher worlds hereafter.
While the traditional Indian Calendar is basically based on lunar positions, but sankranti is a solar event, so while dates of all festivals keep changing, the english calendar date of Makar Sankranti is always same, 14th January.
Makar Sankranti is celebrated in the Hindu Calendar month of Magha. There is another significance of this day, after this day the days start becoming longer & warmer, and thus the chill of winter in on decline