def calculate_reissue_range(start, end):
    """
    Determine what the new validity_start and validity_end dates should be.
    :param start:
    :param end:
    :return:
    """
    span = end - start

    new_start = arrow.utcnow()
    new_end = new_start + span

    return new_start, arrow.get(new_end)

    Determine what the new validity_start and validity_end dates should be.
    :param start:
    :param end:
    :return:
    
lemur/certificates/service.py