I wonder what kind of flowers these are?

I call them "snow flowers" because the come into full bloom right before the first snow storm of the year. My wife put these in about 6 years ago and they are dead most of the year. The leaves start growing in late August and by September they look like a green bush. But every year in October they start blooming and usually fully bloomed one week before the first snowfall. I noticed them this morning about as big as they will get and yes it is snowing in the mountains and will be on the valley floor tomorrow. I think they are asters, but my wife thinks they are mums.