Shouldn't Christians be encouraged to celebrate Christ's birth every day? In fact we should celebrate everything about Christs life and accomplishments... And yet Jehovah’s Witnesses cannot praise him or even thank him for his grace and mercy and sacrifice on our behalf.
Jehovah's Witnesses aren't Christians. They are Christian non-Christians. They think they are Christians... with a ton of cognitive disassociation. It's in the very name of the cult. Jehovah's Witnesses follow Jehovah, not Christ. By the very definition of 'Christian' that makes them 'not Christian'. It never ceases to amaze me at how many people leave the cult but fail to recognize that very important point. JWs don't act like Christians because they aren't Christians.
In answer to the original question... all the responses are correct but there are some exceptions to the rules. People who have one parent in and one parent out, especially if the one that is out is the husband, have some leeway to celebrate holidays.
Also, if you have a congregation with worn out elders they might not do anything to those that celebrate. I was in one congregation where people started celebrating Christmas and even talked about it at the meetings and the elders were too worn down to care. A young overseer came in and livened things up and people just didn't talk about what they celebrated anymore. But the congregation was worn down as well so people got away with a lot more than other congregations I've been a part of. People stopped telling on each other. A lot of the young people left and had no contact with their families. That actually wears pretty hard on people. You have a lot of that and people sometimes stop being so hateful to each other. I'm sure it has changed since then. That was a couple of decades ago.