The Lajnah ad-Da’imah was asked the following question :
Is it permissible to congratulate non-Muslims on the occasion of the new Gregorian year, the new Hijri (lunar) year, and the Mawlid (the Prophet’s birthday)?
It is not permissible to offer congratulations on such occasions, because it is not Mashru‘ (Islamically lawful) to celebrate them.
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.
The Permanent Committee for Scholarly Research and Ifta’
It is also reported that `Abdullah ibn `Amr ibn Al-`As (may Allah be pleased with them both) said, “Anyone who settles in the land of the non-Muslims and celebrates their Nayruz (New Year’s Day) and their Mahrajaan (two non-Islamic Persian festivals), and keeps imitating them until they die in that state, will be gathered with them on the Day of Resurrection.”
[Excerpt From alifta.net]
A Side Note : Shaykh Muhammad bin Saalih al-Uthaymeen mentioned the orgin of the act of celebrating the new years is from the Persians and it is one of their greatest holidays for their Jalaali Calendar. Later, the Christians followed them in that by celebrating the coming of the new gregorian year.
AbdulFattaah bin Uthman