title: Pandas Dataframe filter based on time
body: <p>From the datetime object in the dataframe I created two new columns based on month and day.</p>
  <pre><code>data[&quot;time&quot;] = pd.to_datetime(data[&quot;datetime&quot;])
  data['month']= data['time'].apply(lambda x: x.month)
  data['day']= data['time'].apply(lambda x: x.day)
  </code></pre>
  <p>The resultant data had the correct month and day added to the specific columns.</p>
  <p>Then I tried to filter it based on specific day</p>
  <pre><code>data = data[data['month']=='9']
  data = data[data['day']=='2']
  </code></pre>
  <p>This values were visible in the dataframe before filtering.</p>
  <p>This returns an empty dataframe. What did I do wrong?</p>