title: kdb get last 1 hour records
body: <p>i need to select and get rows which are related to previous 1  and 24 hours. to handle 24 hour i used this code. what about 1 hour how can i get that?</p>
  <pre><code>yesterday = datetime.now() - timedelta(1)
  yesterday = datetime.strftime(yesterday, '%Y-%m-%d')
  
  q.sendSync('{[x;z]select from trades where DateTime &gt; x,symbol=z}', np.datetime64(yesterday,'D'),  np.string_('ETH-USDT'))
  </code></pre>
  <p>kdb saved dataframe</p>
  <pre><code>                     DateTime            symbol  
  0     2022-04-13 12:59:00.171     b'ETH-USDT' 
  1     2022-04-13 12:30:00.171     b'ETH-USDT'   
  2     2022-04-13 10:55:00.171     b'ETH-USDT'       
  3     2022-04-12 10:59:00.171     b'ETH-USDT'  
  4     2022-04-10 10:53:00.185     b'ETH-USDT'  
  5     2022-04-09 10:50:01.114     b'ETH-USDT'  
  </code></pre>