I'm saying that winter starts on december 21st and it has hardly been a month since winter started. There are only 10 days of winter in the month of december.
Well, that depends on if you go by the astronomical definition or not, in which case it does start on the 21st of December.
But in common discussion (as far as I know), many just consider it to go by the months.
December, January and February are Winter. December 1st to February 28/9th
March, April, May are Spring. March 1st to May 31st