[TOMT] [fiction] Sci-fi book with intertwined past and present timelines, storms, theme of nine.

I picked up a new book at a library in 2010, and to the best of my memory is was released some time in 2007-2009, written by an American author.

The book had a theme of nine, e.g. the author had a short chapter on terms involving nine ("dressed to the nines"), etc. and I remember the title having a number in it too. "The Nine Something" or "The Ninth Something". But it might have been eleven? I'm having a heck of a time finding it.

Usually directly before there was some time travel aspect there was also a storm. One timeline was in more or less present day, and another timeline was back before medieval times.

The main character also had a sword or something with knots or notches on it, and jumping through time was linked to the knots.