A simple calculation python source code expiration time

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def time_passed(value):
    now = datetime.now()
    past = now - value
    if past.days:
        return u'%s天前' % past.days
    mins = past.seconds / 60
    if mins < 60:
        return u'%s分钟前' % mins
    hours = mins / 60
    return u'%s小时前' % hours