input: Write a python function to calculate the difference in days between two dates in the format "dd Month yyyy".
  assert diff_in_days("29 June 1999", "29 July 1999") == 30
  assert diff_in_days("01 January 2020", "01 January 2021") == 366
  assert diff_in_days("15 May 2015", "10 May 2015") == -5
output: def diff_in_days(date1, date2):
      from datetime import datetime
      
      date_format = "%d %B %Y"
      d1 = datetime.strptime(date1, date_format)
      d2 = datetime.strptime(date2, date_format)
      
      return (d2 - d1).days