There are many origins of Lohri: all forming part of folklore. However, the main theme of Lohri is the belief that Lohri is the cultural celebration of the winter solstice. According to folk lore, in ancient times Lohri was celebrated on the eve of winter solstice day. It is for this reason that people believe day light is meant to increase from the day after Lohri when the sun starts its northward journey. Accordingly, the day after Lohri is celebrated as Maghi Sangrand from when the days are meant to start getting longer. People believe nights gradually shorten “by the grain of one sesame seed” once the winter solstice passes.
However, instead of celebrating Lohri on the eve of when winter solstice actually occurs, Punjabis celebrate it on the last day of the month during which winter solstice takes place. This is due to linking Lohri to the Bikrami calendar and the twinning of the festival with Makar Sankranti which is celebrated in the Punjab region as Maghi Sangrand. Therefore, Lohri commemorates the passing of the winter solstice.
Scientifically, the shortest day of the year is around 21–22 December with the longest night preceding it on the day before, after which the days begin to get longer. Accordingly, winter solstice begins on 21 December or 22 December and Lohri ought to be celebrated on the longest night before winter solstice day followed by Maghi (Makar) Sangrand on winter solstice which marks the point when daylight will increase.