Berts dagbok (Swedish: Bert's diary), translated as In Ned's Head, is a diary novel, written by Anders Jacobsson and Sören Olsson and originally published in 1987, it tells the story of Bert Ljung from 14 January to 4 June during the calendar year he turns 12 during the spring term in the 5th grade at school in Sweden. Being the first of the Bert Diaries, the term "Berts dagbok" has later even become a term for the entire Bert Universe. The book is the Bert book that has been spread most outside Sweden (as of 2009).