. The year fraction is calculated as:
$$
  \frac{d_1}{{dy}_1} + \frac{d_2}{{dy}_2} + y_2 - y_1 - 1
$$</p>
    </div>

    <pre class="usage"><span class='fu'>actual_actual_isda</span>(<span class='no'>date1</span>, <span class='no'>date2</span>)</pre>

    <h2 class="hasAnchor" id="arguments"><a class="anchor" href="#arguments"></a>Arguments</h2>
    <table class="ref-arguments">
    <colgroup><col class="name" /><col class="desc" /></colgroup>
    <tr>
      <th>date1</th>
      <td><p>A date-time object</