Makara Sankranti / Sankramana significance
Makara Sankranti: Let us first understand what is the meaning of the words 'makara sankranti'. 'Makara' means a 'rashi' and 'sankranti or sankramana' means movement of the Sri Surya Deva (Sun Demi God). Means Sri Surya Deva will move from the 'dhanur rashi' to 'makara rashi'. Here Sankranti / sankramana means moving from one place to another. Sankramana = san + kramana. Here kramana means movement.
Why 14.01.18 shouldn't be considered as 'Makara Sankranti' and why only on 15.01.18 'Makara Sankranti' should be celebrated: Off course on 14th itself the Sri Surya Deva started to move from Dhanur rashi to Makara rashi. But since this movement doesn't happen during the 'Suryodaya' time as per Bharatiya Panchanga we can't consider it as the festival day, as according to Bharatiya samskruti only if something happens during the Suryodaya we consider it as auspicious occasion and correct occasion. On 15th during Suryodaya time, still Sri Surya Deva will be moving towards Makara Rashi and thus all should celebrate 'Makara Sankranti or Makara Sankramana' on 15th only.
Other significances on Makara Sankranti day:
1. Today is the day when Sri Bhisma concludes that he should give away his life after the battle of Sri Kurukhshetra (this he does as he gets confidence that Hastinapura is in the right hands, that with Sri Yudhistira.
2. Today is the day when Sri Surya Deva from 'dakshinayana' (south) moves to 'uttarayana' (north).
3. It is that day when the day of the Devateganam (demigods) starts. From dakshinayana to uttarayana (six months) it is night for Devateganam and similarly from uttarayana to dakshinayana it is day time for Devategan according to their planet. It is exactly like our earth in which evening 6pm to morning 6am is raatri (night) and from 6am to 6pm it is divasa (day).
Shubha Makara Sankranti / Sankarama.
4. With this, it is today that both day and night will be of same and exact time. That is earth's day time is equal to earth's night time. Day time = Night time.
Also here a very important point to be noted is that, since aadi time (unknown time), we had already known about the movement of the Sri Surya Deva (Demi God Sun). ONLY RECENTLY THE EUROPEANS FOUND ABOUT THIS. JUST THINK WHO IS FORWARD IN TECHNOLOGY???
Sri gurubhyo namaha
Om Sri Krishnaaya namaha