title: Date formatting in Google Sheets is not working according to the instructions
body: <p>Yes, I know; this question has been asked thousands of times in hundreds of different places, but Google Sheets stubbornly refuses to let me convert a date such as &quot;9/18/2004&quot; to &quot;2004-9-18&quot;. I select one or more cells whose date format is &quot;dd/mm/yyyy&quot;, click on FORMAT, then NUMBER, then MORE FORMATS, then I select &quot;More date and time formats&quot;, and then select the example &quot;1930-08-05&quot;, and then nothing happens. Nothing changes. I need help with this. Here is a link to the problem column:
  <a href="https://docs.google.com/spreadsheets/d/1gYdPcNO-Jq1SFUpdb88o7KKVqG5_ia9NpD_3T98CkEw/edit?usp=sharing" rel="nofollow noreferrer">https://docs.google.com/spreadsheets/d/1gYdPcNO-Jq1SFUpdb88o7KKVqG5_ia9NpD_3T98CkEw/edit?usp=sharing</a></p>
  <p>Thanks.</p>