title: Python timestamp as index
body: <p>as Im writing my masterthesis at the moment I have to work a with Python for the first time.
  In order to index my data with a timestamp i tried the following which does not really work. Well maybe it does but Iam to stupid to acess the data through the timestemp. Maybe someone can help me to do the next step so that I get acces to the data using the timestamp so that I can slice my yearly data into months for example.</p>
  
  <pre><code>import pandas as pd
  import numpy as np
  import matplotlib.pylab as plt
  from matplotlib import pyplot
  import datetime as dt
  from matplotlib.pylab import rcParams
  import datetime
  rcParams['figure.figsize'] = 15, 6
  
  data = pd.read_csv('PhelixPowerSpotHistory_2015.csv')
  data['Delivery Date']=pd.to_datetime(data['Delivery Date'])
  #data['Time']= pd.to_datetime(data.DeliveryDate)
  #print (data.head())
  print(data.head(10))
  from datetime import datetime
  ts = data['PriceEUR/MWh']
  print(ts.head(10))
  
  
  import matplotlib.pyplot as plt
  plt.plot(ts)
  plt.ylabel('€/MWh')
  plt.xlabel('Delivery Date')
  plt.xticks(np.linspace(0,8721,12))
  plt.show()
  </code></pre>
  
  <p>The head of my data looks like this:</p>
  
  <pre><code>0 2015-01-01 00:00:00         25.02
  1 2015-01-01 01:00:00         18.29
  2 2015-01-01 02:00:00         16.04
  3 2015-01-01 03:00:00         14.60
  4 2015-01-01 04:00:00         14.95
  5 2015-01-01 05:00:00         14.50
  6 2015-01-01 06:00:00         10.76
  7 2015-01-01 07:00:00         12.01
  8 2015-01-01 08:00:00         12.39
  9 2015-01-01 09:00:00         14.04
  </code></pre>
  
  <p>Thanks in advance</p>