The part of the year where it is cold does not start on the shortest day of the year. There is the part of the year that is cold and there’s the part of the year between the shortest day of the year and the equinox, both are winter. Winter doesn’t mean a lot in mild places where you can wear a tshirt out most days of the year. Where it snows, winter is more or less the time of the year where it snows.

People need to relax a little about absolute definitions of things.