Around Clement of Alexandria he disccuses dating in (Stromateis 1.21.144-146):

Yule started out as a month name. In the Germanic calendar, the two months on either side of each solstice had the same name: so the months on either side of the summer solstice were called litha, or alternatively ‘former litha’ and ‘latter litha’, and the months on either side of the winter solstice were…

Tying the fourth day or creation – Genesis 1:14-19 – to increasing daylight hours to the spring equinox: specifically to the 4th day after the spring equinox. (Susan K. Roll, Towards the Origins of Christmas Kampen, Kok Pharos Publishing, 1995: p.64)