title: How to merge datetime colums in Jupyter
body: <p>How can I merge Year, Month and Day to one Year-Month-Day
  How can I merge Hour and minute to hour:minute</p>
  
  <p>I enter code, </p>
  
  <pre><code>import pandas as pd
  import numpy as np
  import matplotlib as mpl
  import matplotlib.pyplot as plt
  from datetime import datetime
  
  df1 = pd.read_csv('D:\charlotte_rg_2003-2014.csv')
  df1.head(3)
  
      Year    Month   Day Hour    Minute  R15
  0   2003    1   1   0   0   0.0
  1   2003    1   1   0   15  0.0
  2   2003    1   1   0   30  0.0
  
  df1['Year-Month-Day'] = 
  pd.to_datetime(df1.Year+'/'+df1.Month+'/'+df1.Day)
  df1['Hour:Minute'] = pd.to_datetime(df1.Hour+':'+df1.Minute,format='%H:%M').dt.strftime('%H:%M')
  df1[['Year-Month-Day','Hour:Minute','R15']]
  </code></pre>
  
  <p>What is wrong? Now I get the error: </p>
  
  <pre><code>~\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\ops.py in na_op(x, y)
     1008         try:
  -&gt; 1009             result = expressions.evaluate(op, str_rep, x, y, **eval_kwargs)
     1010         except TypeError:
   TypeError: ufunc 'add' did not contain a loop with signature matching types dtype('&lt;U21') dtype('&lt;U21') dtype('&lt;U21')
  </code></pre>
  
  <p>Many thank!</p>