title: Distance UTC - LocalTime on Linux
body: <p>I am writing a Linux (Ubuntu and Debian Lenny) application in C++.</p>
  
  <p>Now I need to know the distance/offset between UTC and the currently set system time at a given day in the past. Since I need to convert recorded data, I the distance need to be calculated with respect to a date in the past (which may have a different DST setting than the current day).</p>
  
  <p>Anyone know how to do this?</p>
  
  <p>Edit: Reading the first answer I think I was misunderstood: I do not want to compare dates/times. I have date/time values which I want to convert from UTC to local time. </p>