ay</em> in this way, the <em>time-of-day</em> is
REQUIRED as well.</p>
<p>Finally, you can use the words <strong>now</strong>, <strong>start</strong>, <strong>end</strong> or <strong>epoch</strong> as your time
reference. <strong>Now</strong> refers to the current moment (and is also the default
time reference). <strong>Start</strong> (<strong>end</strong>) can be used to specify a time
relative to the start (end) time for those tools that use these
categories (<strong>rrdfetch</strong>, <a href="././rrdgra