 <p>You could convert to a <a href="http://www.mathworks.com/help/matlab/ref/datenum.html?refresh=true" rel="nofollow"><code>datenum</code></a>:</p> <pre><code>tdiff = datenum(sample.tend) - datenum(sample.tstart) </code></pre> <p>remebering that as <a href="http://www.mathworks.com/help/matlab/ref/datenum.html?refresh=true" rel="nofollow">the docs</a> say:</p> <blockquote> <p>A serial date number represents the whole and fractional number of days from a fixed, preset date (January 0, 0000).</p> </blockquote> <p>so <code>tdiff</code> will be in units of days which is then simple to covert to hours or seconds or whatever you're after. For example to covert to seconds:</p> <pre><code>SecondsPerDay = 24*60*60; tdiffs = tdiff*SecondsPerDay; </code></pre>