Yes,
August 11 and
August 12 seem to be the most common name days for (variants of)
Clare. According to this site's name day pages, it's
August 11 in
France, Germany and Lithuania, and
August 12 in Hungary, Czech Republic, Latvia, Poland, Slovakia, Sweden, Estonia and Finland.
http://www.behindthename.com/namedays/search.php?terms=clairehttp://www.behindthename.com/namedays/search.php?terms=klarahttp://www.behindthename.com/namedays/search.php?terms=klaara