title: ISO Year Week (YYYYww) date format in BigQuery
body: <p>I'm looking for a way to convert dates to ISO Year Week (YYYYww).</p>
  
  <p>I used to use the following in Postgres. Does something similar exist for BigQuery?</p>
  
  <pre><code>to_char( current_date() :: DATE, 'IYYYIW' )
  </code></pre>
  
  <p>The output should have a leading 0 for weeks when applicable.</p>
  
  <p>Cheers,</p>