Celebrating silver, gold or diamond jubilees

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.