input: Write a function to calculate the number of days between two dates.
  assert days_between_dates([2020, 8, 1], [2020, 8, 11]) == 10
  assert days_between_dates([2021, 1, 1], [2021, 1, 1]) == 0
  assert days_between_dates([2019, 12, 31], [2020, 1, 1]) == 1
output: from datetime import datetime
  
  def days_between_dates(date1, date2):
      d1 = datetime(date1[0], date1[1], date1[2])
      d2 = datetime(date2[0], date2[1], date2[2])
      return (d2 - d1).days