 of hours. A 
<code class="code">calendarDuration</code> does arithmetic with &quot;whole&quot; calendar periods.
</p>
<p><code class="code">calendarDuration</code>s and <code class="code">duration</code>s cannot be directly combined, because
they are not semantically equivalent. (This may be relaxed in the future to allow
<code class="code">duration</code>s to be interpreted as numbers of days when combined with
<code class="code">calendarDuration</code>s.)
</p>
<div class="example">
<pre class="example-pr