In ancient times, solstices used to be celebrated by festivals that lasted for several days. The winter solstice marks the longest night of the year, and after that the days start to be longer again gradually. This can be seen as a symbolic return of the sun, and this is the real origin of the holidays celebrated on 24th and 25th of December. This was symbolically celebrated in various cultures in ancient times as the birthdays of sun gods, for example the Egyptian god Ra or Indo-Persian god Mithra. This symbolism of the return of the sun resonates even more nowadays during the Central Sun alignment of the december solstice.