A lot of cultures had festivals at a lot of time periods in the year. For example, the Christian harvest festival generally coincides with the Chinese mid-autumn festival.

The general explanation for Christmas is that Jesus was believed to have been conceived on the 25th of March. Either this is due to it being the spring equinox and “the day the world was created” or because it was believed at one point to be the date He died and thus had a cycle of life thing going on.