Makra Sanskranti ganita is calculated from Surya Kala, when the Sun is in Capricon Period.. there is a reason for this and it has to do with the sangam in Allahabad, do you think they hold the Kumbha Mela by accident at this time of the year, there is always a reason, a scientific reason for this....
Makar Sanskranti has nothing to do with the Winter Solstice.. and Indian Astrology is not an off shoot of tropical western astrology.. One needs a Guru in Jyotisha it is not something learned from books and boxed in a western mind of one word translation from ancient sanskrit in where one word equals a universe of teachings. Look at the scale of the earth to the sun.. it is not comparable. There are many levels and layers not even understood here in the west.. do not take any book translation as literal.
Makara Sanskranti is calculated from Surya, when Surya specifically enters Capricorn 'Period'. not when the sun is in Sagitarius or how we would like to fit the Indian ways into a box to fit our western brain. There is not mistake and herein lies the problem of trying to compare apples to turnips.. Do not get your information from Wikipedia when it comes to learning Jyotisha.