In discussing the minhagim of Nittelnacht with a few people, I was told that Rav Chaim Volozhin "abolished" Nittelnacht. I don't know why Chaim Volozhiner would have any shaychis to Nittelnacht at all, that he would have to "abolish" it, but does anyone know of any sources that discuss Rav Chaim Volozhiner's dealing with Nittelnacht?
he held that someone must be learning torah 24/7 or else world would cease to be. unless he held that it only goes from shkia until chatzos (in which case the 8.5 hour time difference between the u.s. east coast and iran would take care of it), as opposed to chatzos yom of erev christmas to chatzos layla, advocating that everyone should observe nittelnacht would be advocating that there be a time that the world stop learning. however, perhaps he only held that it should be observed in places with a christian population, which many sefardic lands do/did not.
(or it was no longer dangerous to go to the beis in his time/if he abolished not learning entirely it was probably b/c he felt it was a minhag shdus which possibly gives credence to avoda zara)