<p dir="auto">In pandas 0.13.1 this code produces a plot that, when "moused over", indicates incorrect dates on the 't' (x) axis, despite having the correct axis label.</p>
<div class="highlight highlight-source-python notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="pd.Series([1, 2, 3], index=pd.date_range('2014-01-01', periods=3, freq='D')).plot()"><pre class="notranslate"><span class="pl-s1">pd</span>.<span class="pl-v">Series</span>([<span class="pl-c1">1</span>, <span class="pl-c1">2</span>, <span class="pl-c1">3</span>], <span class="pl-s1">index</span><span class="pl-c1">=</span><span class="pl-s1">pd</span>.<span class="pl-en">date_range</span>(<span class="pl-s">'2014-01-01'</span>, <span class="pl-s1">periods</span><span class="pl-c1">=</span><span class="pl-c1">3</span>, <span class="pl-s1">freq</span><span class="pl-c1">=</span><span class="pl-s">'D'</span>)).<span class="pl-en">plot</span>()</pre></div>
<p dir="auto"><a target="_blank" rel="noopener noreferrer nofollow" href="https://camo.githubusercontent.com/6dd5fc1e3be5a34400c7a3def8a8ddac54459da6107dd08ead808126092b244a/68747470733a2f2f662e636c6f75642e6769746875622e636f6d2f6173736574732f353335363334302f323430353837392f38663764326566362d616135632d313165332d396336382d6631333833656663366235322e706e67"><img src="https://camo.githubusercontent.com/6dd5fc1e3be5a34400c7a3def8a8ddac54459da6107dd08ead808126092b244a/68747470733a2f2f662e636c6f75642e6769746875622e636f6d2f6173736574732f353335363334302f323430353837392f38663764326566362d616135632d313165332d396336382d6631333833656663366235322e706e67" alt="screenshot" data-canonical-src="https://f.cloud.github.com/assets/5356340/2405879/8f7d2ef6-aa5c-11e3-9c68-f1383efc6b52.png" style="max-width: 100%;"></a></p>
<p dir="auto">(matplotlib version is 1.3.1)</p>
<p dir="auto">After using the <code class="notranslate">asfreq</code> method to change the frequency of a time-series DataFrame from <code class="notranslate">None</code> to something e.g. <code class="notranslate">15Min</code> the cursor position in matplotlib graphs of that DataFrame is no longer correct (usually shows a datetime just after the unix epoch).  The following demonstrates this (NB dt in df1 is not a constant):</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="df1 = pandas.read_csv('tseries1.csv', names=['tstamp', 'Q'], parse_dates=True, 
    index_col='tstamp').clip_lower(0).fillna(0)
df1['T'] = pandas.read_csv('tseries2.csv', names=['tstamp', 'T'], parse_dates=True, 
    index_col='tstamp', squeeze=True).clip_lower(0).fillna(0)

df2 = df1.asfreq(freq='15Min', method='ffill')
# NB df1.index.freq is None
# NB df2.index.freq is &lt;15 * Minutes&gt;
df1.plot()
df2.plot()
plt.show()"><pre class="notranslate"><code class="notranslate">df1 = pandas.read_csv('tseries1.csv', names=['tstamp', 'Q'], parse_dates=True, 
    index_col='tstamp').clip_lower(0).fillna(0)
df1['T'] = pandas.read_csv('tseries2.csv', names=['tstamp', 'T'], parse_dates=True, 
    index_col='tstamp', squeeze=True).clip_lower(0).fillna(0)

df2 = df1.asfreq(freq='15Min', method='ffill')
# NB df1.index.freq is None
# NB df2.index.freq is &lt;15 * Minutes&gt;
df1.plot()
df2.plot()
plt.show()
</code></pre></div>
<p dir="auto">I find the Matplotlib cursor position to be invaluable when looking for features in very long time-series.</p>
<p dir="auto">Versions:</p>
<ul dir="auto">
<li>pandas master (commit ID <a class="commit-link" data-hovercard-type="commit" data-hovercard-url="https://github.com/pandas-dev/pandas/commit/764b4446820f1bcd6463cf7eeda9e16234713949/hovercard" href="https://github.com/pandas-dev/pandas/commit/764b4446820f1bcd6463cf7eeda9e16234713949"><tt>764b444</tt></a>)</li>
<li>numpy 1.8</li>
<li>matplotlib 1.3.0</li>
</ul>