I don't know what you mean exactly as the time element being the 'variable', but it's literal translation is 'spirit of the times' - were you looking for something other than this? I can't quite understand your question.
I think genius loci is the phrase you're after, but it's pretty rare and won't be widely understood (I don't think it really has a 'common usage'). It might be simpler, if possible, just to say 'the spirit of London' - or Paris, or Marrakech, or wherever.