title: AttributeError: 'numpy.int64' object has no attribute 'to_timestamp'
body: <p>I am trying to plot a time series from a python data frame. The code is below.</p>
  
  <pre><code>import requests
  from bs4 import BeautifulSoup
  import pandas as pd
  import datetime
  import pandas as pd
  import numpy as np
  import matplotlib.pyplot as plt
  from matplotlib.dates import DateFormatter, YearLocator, MonthLocator
  plt.style.use('ggplot')
  
  
  def plot(df, filename, heading=None):
  
      fig, ax = plt.subplots(figsize=(8, 4))
  
      min_date = None
      max_date = None
      for col_name in df.columns.values:
  
          # plot the column
          col = df[col_name]
          col = col[col.notnull()] # drop NAs
          dates = [zzz.to_timestamp().date() for zzz in col.index]
          ax.plot_date(x=dates, y=col, fmt='-', label=col_name,
              tz=None, xdate=True, ydate=False, linewidth=1.5)
  
          # establish the date range for the data
          if min_date:
              min_date = min(min_date, min(dates))
          else:
              min_date = min(dates)
          if max_date:
              max_date = max(max_date, max(dates))
          else:
              max_date = max(dates)
  
      # give a bit of space at each end of the plot - aesthetics
      span = max_date - min_date
      extra = int(span.days * 0.03) * datetime.timedelta(days=1)
      ax.set_xlim([min_date - extra, max_date + extra])
  
      # format the x tick marks
      ax.xaxis.set_major_formatter(DateFormatter('%Y'))
      ax.xaxis.set_minor_formatter(DateFormatter('\n%b'))
      ax.xaxis.set_major_locator(YearLocator())
      ax.xaxis.set_minor_locator(MonthLocator(bymonthday=1, interval=2))
  
      # grid, legend and yLabel
      ax.grid(True)
      ax.legend(loc='best', prop={'size':'x-small'})
      ax.set_ylabel('Percent')
  
      # heading
      if heading:
          fig.suptitle(heading, fontsize=12)
      fig.tight_layout(pad=1.5)
  
      # footnote
      fig.text(0.99, 0.01, 'nse-timeseries-plot', ha='right',
          va='bottom', fontsize=8, color='#999999')
  
      # save to file
      fig.savefig(filename, dpi=125)
  
  
      url = "https://www.google.com/finance/historical?cid=207437&amp;startdate=Jan%201%2C%201971&amp;enddate=Jul%201%2C%202017&amp;start={0}&amp;num=30"
      how_many_pages=138
      start=0
  
      for i in range(how_many_pages):
          new_url = url.format(start)
          page = requests.get(new_url)
          soup = BeautifulSoup(page.content, "lxml")
          table = soup.find_all('table', class_='gf-table historical_price')[0]
  
          columns_header = [th.getText() for th in table.findAll('tr')[0].findAll('th')]
          data_rows=table.findAll('tr')[1:]
          data=[[td.getText() for td in data_rows[i].findAll(['td'])] for i in range(len(data_rows))]
  
          if start == 0:
              final_df = pd.DataFrame(data, columns=columns_header)
          else:
              df = pd.DataFrame(data, columns=columns_header)
              final_df = pd.concat([final_df, df],axis=0)
          start += 30
          final_df.to_csv('nse_data.csv', sep='\t', encoding='utf-8')
  
  
      plot(final_df,'nsetsplot')
  </code></pre>
  
  <p>When I run the code I get the error
  <code>AttributeError: 'numpy.int64' object has no attribute 'to_timestamp'</code></p>
  
  <p>when I do </p>
  
  <p><code>dates = [zzz.to_timestamp().date() for zzz in col.index]</code></p>
  
  <p>I am using Anaconda 64-bit on Windows 7 (x86_64)</p>