Haven't done it yet...but usually mount the dedicated winter tires (18" Michelin X-Ice xi2) sometime between Thanksgiving and New Years. Last year...it was warm enough to get by until the last day of the year.
Since we got a good snow flurry last Saturday...looks like the snows might have to go on before Xmas.
BTW, I like them not just for snow...but anytime the temps remain below 45° F...it can be dry, rain, sleet, or snow...the Michelins just perform better than my 20" Nitto Motivos.