input: Write a python function to calculate the number of days between two dates.
  assert calculate_days_between(datetime(2023, 1, 1), datetime(2023, 1, 10)) == 9
  assert calculate_days_between(datetime(2020, 2, 28), datetime(2020, 3, 1)) == 2
  assert calculate_days_between(datetime(2022, 12, 31), datetime(2023, 1, 1)) == 1
output: from datetime import datetime
  
  def calculate_days_between(date1, date2):
      delta = date2 - date1
      return delta.days