Some are only half hardy so I would treat it as such!

I would leave it in its current pot in a frost free area, only watering to keep it from drying out completely!

Then in spring when all fear of frost is gone and the new growth* is emerging then you can safely plant it outdoors!

* You can take basal cuttings of this young growth and increase your stock!

See here;
http://www.thegardenersalmanac.co.uk/Data/Chrysanthemum/Chrysanthemum.htm

Or in Spring you can trim it to about 3 or 4 inches, feed it and get it growing again. It may be taller in year 2 as they are often treated to keep them compact (this makes them easier for shops to handle).