      <th>sep</th>
      <td><p>Character string that separates the <code>start_format</code> and the
<code>end_format</code>.</p></td>
    </tr>
    <tr>
      <th>end_offset</th>
      <td><p>Units in days if <code>x</code> is <code>Date</code>, or in seconds if
<code>x</code> is <code>POSIXct</code> or <code>POSIXlt</code>.
Will be subtracted from the end of each period.
If 0, the end of the previous period is equal to the start of the next.</p></td>
    </tr>
    <tr>
      <th>units_to_last</th>
      