title: airflow TriggerDagRunOperator how to change the execution date
body: <p>I noticed that for scheduled task the execution date is set in the past according to </p>
  
  <blockquote>
    <p>Airflow was developed as a solution for ETL needs. In the ETL world,
    you typically summarize data. So, if I want to summarize data for
    2016-02-19, I would do it at 2016-02-20 midnight GMT, which would be
    right after all data for 2016-02-19 becomes available.</p>
  </blockquote>
  
  <p>however, when a dag triggers another dag the execution time is set to now().</p>
  
  <p>Is there a way to have the triggered dags with the same execution time of triggering dag? Of course, I can rewrite the template and use yesterday_ds, however, this is a tricky solution.</p>