title: Running airflow DAG with proper scheduling
body: <p>I am working with Airflow and having issues for scheduling my DAG's. I have a DAG which I want to run at every Sunday at 00:00 and here is my code</p>
  
  <pre><code>args = {
  'owner': 'rsabbir',
  'depends_on_past': False,
  'start_date': datetime(2018, 2, 22, 00, 00),
  'retry_delay': timedelta(minutes=1)
  }
  
  dag = DAG(
      dag_id='DAG_column_encoding', default_args=args, schedule_interval='* * * * 0')
  </code></pre>
  
  <p>I've tried with a different 'start_date' from last week but the task didn't run during weekend. There is also another DAG which I want to run at a particular time(4:30 AM) everyday and I have this code.</p>
  
  <pre><code>args = {
  'owner': 'rsabbir',
  'depends_on_past': False,
  'start_date': datetime(2018, 2, 21, 00, 00),
  'retry_delay': timedelta(minutes=1)
  }
  
  dag = DAG(
      dag_id='DAG_vacuum_tables', default_args=args, schedule_interval='30 4 * * */1')
  </code></pre>
  
  <p>Both of them are not working as expected. I have gone through the Airflow documentation but haven't understood how these different cases fo scheduling work. </p>
  
  <p>Can anyone give me a brief idea about how these 'start_date' and 'schedule_interval' actually work together in airflow? Is there any other effective way to work with these two parameters in airflow?</p>