Christmas, or Xmas for non-believers, used to be a quiet period in Edinburgh. It's less so now, although (Edinburgh's Hogmanay aside) it's still not quite as mad as the hurlyburly of the Edinburgh Festival in August.
Edinburgh's Hogmanay is a four-day winter festival that takes place at the end of each year. In 2009-2010, the Hogmanay festival has an additional day.
