Graham - agreed 'shortest' it is. I was fooled to begin with because 21st Dec is 'solstice' day and of course the 'S' word has 8 letters. As I said I couldn't see how this worked then realised the correct word.
Think of a Belgian artist (modern/surreal) ~ take 'leaders' of Modern Art away (ie they leave) his surname and put what's left around usual abbreviation for home counties - you then get a term for a "Parisienne". ;-)