title: Find out the time since unix epoch for a certain date time?
body: <p>I want to find out the time in unix time (ie seconds since the unix epoch) on 9:00 BST on 1st October 2009. How can I do this on the linux command line?</p>
  
  <p>I know you can use <code>date @$UNIXTIME '+%someformat'</code>, but the unix time is what I'm trying to figure out</p>