This related question explains what this minhag is and a couple of reasons for it.
I was wondering to what extent is this minhag practiced today apart from Chabad (see
Hayom Yom - 17 Tevet)...do all Chasidim have this minhag?... because I heard that one branch of Chasidim practice this on a different day altogether (some time in January) because that was when the Christians of their area celebrated that festival.
Also is it practiced in all parts of the world - even in places which never officially celebrated the 25 of December.