Are wedding anniversaries an innovation?
Some young couples, when the date of their wedding comes around again, like to celebrate that day. The husband often presents a romantic and affectionate gift to his wife. Sometimes, they rent a room in a hotel for the night and spend a romantic time together.
Some Muslims, however, look upon this with suspicion, wondering if this comes under the prohibition of observing holidays aside from the established `ids.
Celebrating one's anniversary in the manner described above is not in any way intended as a religious observance. I see no objection to it at all.
There is no way that the question of innovation can even come up, since an innovation in Islam is to introduce something unprecedented into a matter of religious observance or a matter of devotion to Allah.
As long as the observance of one's wedding anniversary is just a customary occasion - neither intended as an expression of religious worship nor established as a formal festival or rite - then there is nothing wrong with celebrating it.
And Allah knows best.