Celebrations in ISLAM

What’s the issue of celebrating certain cultural events, that has nothing to do with religion? That’s to say, would celebrating Birthdays, New Years or maybe Independence day be HARAM? I know (at least I heard) birthdays are a no go zone for Muslims, but why is it? What about the other celebrations, I have mentioned. As a matter of fact, how do we define celebration in Islam? In general, a celebration can be thought of as going to the movies or eating out for dinner with family as a way of celebrating and rewarding yourself for good grades in exams. A celebration can also be thought of as crowds of people coming together establishing cultural carnivals….. Which definition/if any other, does ISLAM favours?