Well, there is a "Christmas tree" in the background and they are wearing red nisse hats, so obviously they are celebrating the birth of middle eastern jew. ;p

Good question. I have had fun as this meme pic represents in my life at a past time but not today. Was I celebrating? Maybe not. If drinks were involved and the family all together with gifts, etc. it certainly was not about the birth of someone who is going to take you "sins" away. There is nothing in the scriptures that theists hold so dear that even hints at it. Of course they will tell you that "the wise men brought gifts" but all that does is support merchant day. What are they celebrating?