Is it ok to celebrate New Years Eve? Which (orthodox, not modox or non-orthodox) rabbinical authority was against it and which one was in favor of it (if such opinions exist).
I'm creating an extra answer, since this is specific to this year, which is unique. New Year's coincides with 10 Tevet - a serious fast day. As a matter of fact, 10 Tevet begins before the onset of New Year's. While it is true that the fast itself starts at the onset of daylight, nonetheless, the memory of the tremendous tragedy begins at sunset several hours prior to midnight (12 AM, not "halachic" midnight).
See this article for a viewpoint, that I agree with for this year - contrary to my previous answer. Excerpt:
Last week we celebrated Hanukkah – the restoration of Jewish sovereignty, the restoration of once again living our national life according to our own calendar.
And this brings us back to the 10th of Tevet, which this year coincides with the Gregorian new year. It is distressing indeed to see Jews celebrating this day – as if it has any significance for us whatsoever! It is bad enough when Jews in the USA and Europe and other countries of exile hold new year’s parties on the 1st of January. But mired in exile, forced by circumstances to live their lives according to the Gregorian calendar – what else can we expect?
It is infinitely worse that Jews here in Israel have brought this paganism (yes, overt paganism) into our own country.
We often hear the casual excuses: It’s not a religious celebration; it’s simply an excuse for a party; it has no Christian or pagan significance. It is usually possible to conveniently ignore the contradiction.
But this year, the decision is starker. This year, for the first time since 5699 (1939), the 1st of January, Sylvester, coincides with the fast of the 10th of Tevet.
The choice is far more blatant. Fast or feast? Mourn over the destruction of Jerusalem? Or celebrate this highly unsavoury pope and “saint”, who was instrumental in convincing the Roman Emperor Constantine I, the first Christian Emperor of Rome, to prohibit Jews from living in Jerusalem.
Live and celebrate according to a foreign calendar, instituted by Pope Gregory XIII – as vicious a Jew-hater as any pope? Or live and mourn and celebrate according to our calendar, for which the Macabbees fought?
The choice is yours.
It depends what you mean by "celebrate".
Acknowledging that this is your (the Jewish) New Year may be problematic, as we follow our soli-lunar / Judaic calendar and not the Gregorian calendar. I.e. - it may be problematic to wish other Jews "Happy New Year" with the thinking that it is the start of a New (Jewish) Year. If it's clear to you and the recipient that you mean the Gregorian year, then, there's no problem.
As for other related celebrations, see my answer to New Year's Fireworks which mentions Rabbi Feinstein's and other views on this.
It is understood that getting drunk to the point where you misbehave, and G-d forbid become a personal or public danger, is forbidden at all times, and New Year's celebration is certainly no excuse.