Christmas is a complex and multi-layered celebration and feast.
Christians are correct in pointing out that it is most importantly about remembering and celebrating the Birth of Christ; but neo-pagans and other non-Christians are also correct that there was already a Winter Solstice-related feast before Christ - and this remains an important aspect of the event, especially in relation to the character of Father Christmas or Santa Claus.
I have nearly always found Christmas to be a special time of year, including when I was not a Christian; but being Christian certainly adds roots, significance and reality to the occassion.
The pre-Christian aspects could be termed both astronomical and biological. The astronomical aspect is presumably a consequence of Christmas being just after the Winter Solstice; and suggests that there must have existed a sophisticated scientific priesthood able to measure the length of days; and detect when the shortest day had just been passed so they could begin to organise a celebration of the (true) New Year.
The biological aspect was that there was still plenty of stored food and fuel to stage a feast - only tempered by the need to keep enough in store to see enough people through the 'hungry gap' of spring, and until the next growing season brings fresh supplies.
These are good reasons for a post-Solstice celebratory feast - but this would be of spiritual significance only insofar as there was a society where Sun and The Light were accorded the status of deity. The aptness for celebrating the birth of Christ is obvious; and the cultural elaboration of the Nativity story created a very special time of year: when the spiritual comes closer to the everyday than at any other point of the calendar.
Let us all at Christmas be sensitively aware of this fact; and alert for those communications and intuitions which we may now most confidently expect.