What would be the ruling on birthdays? Is it something that is only for the kuffar or is it considered worldwide tradition? May Allah reward you
It is closer to being a custom that does not fall under the issue of innovation because it is unrelated to worship or the religion. So if children for example were exchanging gifts or having a gathering with friends, then there is scope for this, as long as it is not taken beyond the boundaries of Shariah nor taken to excess. And this is the fatwa given by a number of our scholars, Hanbalis and otherwise.
And Allah knows best