Answer:
In Portugal people do the Ceia de Natal which is comparable to the North American Thanksgiving meal although Ceia de Natal does not end in the dinner. Ceia de Natal takes place in Christmas Eve and consists in a dinner, supper and tables full of food, cakes and all type of sweets that accompanist the party till as late as 3 am. At dinner it is traditional to eat cod fish throughout the country, but some families eat octopus or in a less common side turkey. Traditional Christmas cakes and sweets are vast (as an example: Filhós, Rabanadas, Aletria, Tronco de Natal, Bolo Rei, Lampreia). In a personal note cinnamon always reminds me of Christmas since some of the most well known Christmas sweets have cinnamon in them. Missa do Galo is the Christmas Mass (catholic faith) and it happens after dinner and is attended by the most religious families (not very common in big cities). Portuguese change gifts at midnight at Christmas Eve not on Christmas Morning.
In this sense one may say that Christmas most important moment is on Christmas Eve as its an occasion when entire families are together in the Ceia de Natal. On Christmas day it is tradition to dress new clothes and its common to make small trips around the city/country doing sightseeing. In interior places and small places it is common to see Religious Processions taking place.