Do Seventh day Adventists celebrate Christmas, and if not WHY?

Answer 1

I actually am not 7th day, but I know some people who are. I don't believe they celebrate Christmas. They don't because the date of Christmas is not in the bible. They only celebrate Easter which can be calculated based on the date of the Jewish festival that was being celebrated at the time of Jesus' death.
The date of Christmas, in case you didn't know, was actually decided upon by Pope Gregory in an attempt to get more pagan to convert to Christianity by placing it on the same date as the traditional birth of Mithras, a perian god of light, whose birth story is a lot like the story in Luke.