title: Extra operand 'ago' when trying to parameterize bash date
body: <p>I'm following <a href="https://unix.stackexchange.com/questions/382099/bash-date-d-throws-invalid-date-when-date-is-parameterized">this example</a> to parameterize date. But this code:</p>
  
  <pre><code>FROM_DATE=$(date --date='1 day ago' +"%F")
  
  OPTARG="1 day ago"
  echo $OPTARG
  FROM_DATE=$(date --date=${OPTARG} +"%F")
  echo $FROM_DATE
  </code></pre>
  
  <p>gives me an error:</p>
  
  <pre><code>date: extra operand ‘ago'’
  </code></pre>
  
  <p>How should I fix it?</p>