title: Airflow : dag run with execution_date = trigger_date = fixed_schedule
body: <p>in airflow, I would like to run a dag each monday at 8am (the execution_date should be of course "current day monday 8 am"). The relevant parameters to set up for this workflow are :</p>
  
  <ul>
  <li><code>start_date</code> : "2018-03-19"</li>
  <li><code>schedule_interval</code> : "0 8 * * MON"</li>
  </ul>
  
  <p>I expect to see a dag run every monday at 8am . The first one being run the 19-03-2018 at 8 am with <code>execution_date</code> = 2018-03-19-08-00-00 and so on each monday.</p>
  
  <p>However it's not what happens : the dag is not started  on 19/03/18 at 8 am. The real behaviour is explained here for exemple : <a href="https://stackoverflow.com/a/39620901/1510109">https://stackoverflow.com/a/39620901/1510109</a> or <a href="https://stackoverflow.com/a/48213964/1510109">https://stackoverflow.com/a/48213964/1510109</a>
  The behaviour is  : at each end of the interval ( weekly in my case) the dag is run with execution_date = beginning of the interval (i.e the previous week). This behavour is apparently motivated by an "ETL way of thinking" (see the link above). But it's absolutely not what I want. </p>
  
  <p>How what can I achieve to run my dag each monday at 08:00am with <code>execution_date</code>  = <code>trigger_date</code> = now ( = current monday 8am) ?</p>
  
  <p>Thanks</p>