title: Sleep until a specific time/date
body: <p>I want my bash script to sleep until a specific time. So, I want a command like "sleep" which takes no interval but an end time and sleeps until then.</p>
  
  <p>The "at"-daemon is not a solution, as I need to block a running script until a certain date/time.</p>
  
  <p>Is there such a command?</p>