title: What is the difference between CURRENT and TODAY in Informix
body: <p>I am junior in informix and I am struggling with some date calculations. I have this code snippet in my source:</p>
  
  <pre><code>LET dtRefDate = TODAY;
  
  IF extend( CURRENT, hour to hour ) BETWEEN '06' AND '23'  THEN LET
     dtRefDate = TODAY+1;
  END IF;
  </code></pre>
  
  <p>Can anybody explain me please what does extend function do? and what is the difference between CURRENT and TODAY? I didn't comprehend the difference from IBM official documentation. 
  Thank you</p>