It is not permissible to hold parties and give gifts and so on, on the occasion of a number of years having passed since the opening of a store, school or any other kind of venture, because this is introducing innovated festivals into Islam, and because it is an imitation of the disbelievers who do such things. It is essential not to do that and to avoid it. End quote. 

Fataawa al-Lajnah al-Daa’imah, 2/261 

Shaykh Bakr Abu Zayd said in his book ‘Eid al-Yoobeel (Jubilees), p. 25: 

Celebrating jubilees of various kinds and with various aims is a celebration that has been introduced into the religion (an innovation) and is contrary to the command of the Lord of the Worlds, and is an imitation of the disbelievers and venerating that which they hold sacred. 

Those who forbid and speak against innovated celebrations -- including celebrating the birthday of the Prophet (blessings and peace of Allah be upon him), the night of the Isra’ and Mi’raaj, the new hijri year, and other innovated celebrations observed by some Muslims which have been introduced by those who seek to misguide others -- their first priority must be to announce the prohibition on celebrating jubilees, whether they are silver, golden, diamond, eightieth, for any length of time, for any place, for any person, for any occasion. Whoever does not do that is confused and contradicting himself, whether he likes it or not, and this comes under the heading of following whims and desires. End quote. 

And Allah knows best.