import datetime
from dateutil.relativedelta import relativedelta


def time_delta_hr(start, end):
    """
    Return a string of human readable time delta.
    """

    start_date = datetime.datetime.fromtimestamp(start)
    end_date = datetime.datetime.fromtimestamp(end)
    delta = relativedelta(end_date, start_date)

    attributes = ['years', 'months', 'days', 'hours', 'minutes', 'seconds']

    result = []
    for attribute_name in attributes:
        attribute = getattr(delta, attribute_name)
        if attribute > 0:
            result.append('%d %s' % (attribute, attribute_name))

    return ', '.join(result)