old_contents: from datetime import date, timedelta
  
  
  def get_cutoff_date(days):
      """Calculate the cutoff date or return None if no time period was set."""
      if days is None or type(days) != int:
          return None
      else:
          if days >= 0:
              return date.today() - timedelta(days=days)
          else:
              return None
  
new_contents: from datetime import date, timedelta
  
  
  def get_cutoff_date(days):
      """Calculate the cutoff date or return None if no time period was set."""
      if days is None or type(days) != int:
          return None
      else:
          if days > 0:
              return date.today() - timedelta(days=days)
          elif days == 0:
              return date.today() + timedelta(days=2)
          else:
              return None
  
subject: Make it so a cutoff of 0 leads to no invites/registrations being shown.