title: How to make pandas.read_excel with engine='openpyxl' behave like it did with xlrd, not showing nanoseconds by default?
body: <p>We have a process that reads data in from an Excel .xlsx spreadsheet into a pandas DataFrame.  While trying to upgrade to the latest version (1.2.1) of pandas, I saw the following in the doc for pandas <code>read_excel</code> function for the <code>engine</code> argument:</p>
  <blockquote>
  <ul>
  <li>“openpyxl” supports newer Excel file formats.</li>
  </ul>
  </blockquote>
  <blockquote>
  <p>Changed in version 1.2.0: The engine xlrd now only supports old-style .xls files.</p>
  </blockquote>
  <p>So, I added <code>engine='openpyxl'</code> to my <code>read_excel</code> function call and started to see strange, new behavior, whereby datetime values now were showing nanoseconds by default, which wasn't the case with <code>xlrd</code>.  On top of that, I was seeing datetimes a bit off from the expected value seen in Excel by a few nanoseconds. I saw the same thing with pandas 1.2.1 and also 1.1.4.</p>
  <p>For the following Excel data <em>(the raw values show as 44098.0416666667 for the 9/24 date and 44083.6847222222 for both 9/9 dates)</em></p>
  <p><a href="https://i.stack.imgur.com/qasQW.png" rel="noreferrer"><img src="https://i.stack.imgur.com/qasQW.png" alt="enter image description here" /></a></p>
  <p>I'm seeing the following behavior:</p>
  <pre><code>&gt;&gt;&gt; import pandas as pd
  &gt;&gt;&gt; pd.read_excel('~/testDatetimeNanos.xlsx')
               TestDate
  0 2020-09-24 01:00:00
  1 2020-09-09 16:26:00
  2 2020-09-09 16:26:00
  &gt;&gt;&gt; pd.read_excel('~/testDatetimeNanos.xlsx', engine='openpyxl')
                      TestDate
  0 2020-09-24 01:00:00.000003
  1 2020-09-09 16:25:59.999998
  2 2020-09-09 16:26:00.000000
  </code></pre>
  <p><strong>I'm wondering if there's a way to use the new openpyxl engine so that its behavior is consistent with the old xlrd engine...?</strong><br />
  <em>Also, wondering if I may have stumbled onto a bug (update: submitted <a href="https://github.com/pandas-dev/pandas/issues/39599" rel="noreferrer">bug report</a>).</em></p>
  <p><strong>As of openpyxl ≥3.0.7, the bug has been fixed (Aug 2021)</strong></p>