title: Airflow: How can use macros to get the first day of last month?
body: <p>I am trying to backfill a job that requires the date to be tuned to the first day of last month.</p>
  
  <p>I could use:</p>
  
  <pre><code>from datetime import datetime, timedelta, date
  
  date = (date.today().replace(day=1) - timedelta(days=1)).replace(day=1)
  </code></pre>
  
  <p>But I am not sure if the backfill in Airflow will return date.today() as the day of the run.</p>