title: Is there a way to backfill historical data (once) for a new Flow in Prefect?
body: <p>I just started reading about Prefect (and have a little experience using Airflow).</p>
  <p>My goal is to set a task which runs daily in Prefect and collects data to a folder (I guess that's what Prefect can help me do for sure).
  Also my goal is to populate the historical data (as if I ran this job back in time).</p>
  <p>In Airflow there is this concept of start_date which when set in the past, the DAG will run since that date and populate on each interval.</p>
  <p>For example, if I have a task which takes a date and returns the data for that date, such as:</p>
  <pre><code># Pseudo code
  def get_values_from_somewhere(date: datetime) -&gt; dict:
      return fetched_values_in_json(date)
  </code></pre>
  <p>Is there a native way to do this in Prefect?
  I could not find this answered anywhere in here or the docs, though backfilling is mentioned <a href="https://docs.prefect.io/core/faq.html#does-prefect-support-backfills" rel="nofollow noreferrer">here</a>.
  Any help / guidance will be super useful.</p>
  <p>What I tried:</p>
  <p>When I set <code>schedule</code> to be:</p>
  <pre><code>from datetime import datetime, timedelta
  
  from prefect.schedules import Schedule
  
  schedule = Schedule(clocks=[IntervalClock(interval=timedelta(hours=24), start_date=datetime(2019, 1, 1))])
  </code></pre>
  <p>and then I do <code>flow.run()</code> I simply get:</p>
  <pre><code>INFO:prefect.My-Task:Waiting for next scheduled run at 2020-09-24T00:00:00+00:00
  </code></pre>
  <p>What I was expecting is to run since the <code>start_date</code> which I have provided and then pause until it reaches present time and wait for the next schedule.</p>