title: What is the difference between %X and %x in format-time-string?
body: <p>What is the difference between "%X" and "%x" in following the functions?!</p>
  
  <pre><code>(defvar insert-time-format "%X" 
  "*Format for \\[insert-time] (c.f. 'format-time-string').")
  
  -----------
  
  (defvar insert-date-format "%x"
  "*Format for \\[insert-date] (c.f. 'format-time-string').")
  </code></pre>