title: Pandas date_range and leap years
body: <p>When running this code:</p>
  
  <pre><code>a = pd.date_range("1959-12-09 00:00:00", "2013-12-09 12:00:00", freq = "365D6H")
  weekDays = [dt.datetime.weekday(d) for d in a]
  df = pd.DataFrame({"Date": a, "Jour": weekDays})
  df.head(6)
  </code></pre>
  
  <p>I'm getting:</p>
  
  <pre><code>0 1959-12-09 00:00:00     2
  1 1960-12-08 06:00:00     3   * 
  2 1961-12-08 12:00:00     4
  3 1962-12-08 18:00:00     5
  4 1963-12-09 00:00:00     0
  5 1964-12-08 06:00:00     1   *
  6 1965-12-08 12:00:00     2
  </code></pre>
  
  <p>and so problems with leap years. 
  How could I do to have exactly one calendar year between dates in spite of leap years ?</p>