star gazing - Is the location that published calendars use to calculate the seasons one specific location on the earth?

Astronomical events such as the solstices and equinoxes occur at a specific instance in time on a specific day, often given in Universal Time.

For example, this winter's solstice occurs on 21 Dec 2014 at 23:03 Universal Time. Since most of Europe is an hour ahead, this may occur on 22 Dec 2014 at 00:03 (and subsequent hours) given in local time based on the time zone. So British and American calendars will show the solstice occurring on 21 Dec, and in countries east of Greenwich on 22 Dec.