title: TypeError: Timestamp subtraction
body: <p>I have a script that goes and collects data.  I am running into the <code>TypeError: Timestamp subtraction must have the same timezones or no timezones</code> error. I have looked at other postings on this error, but had trouble finding a solution for me.  </p>
  
  <p>How can I bypass this error. Once the data is collected, I don't manipulate it and I don't quite understand why I cannot save this <code>dataframe</code> into an excel document.  Can anyone offer help?</p>
  
  <pre><code>import pandas as pd
  import numpy as np
  import os
  import datetime
  import pvlib
  from pvlib.forecast import GFS, NAM
  
  #directories and filepaths
  barnwell_dir = r'D:\Saurabh\Production Forecasting\Machine Learning\Sites\Barnwell'
  barnwell_training = r'8760_barnwell.xlsx'
  
  #constants
  writer = pd.ExcelWriter('test' + '_PythonExport.xlsx', engine='xlsxwriter')    
  time_zone = 'Etc/GMT+5'
  barnwell_list = [r'8760_barnwell.xlsx', 33.2376, -81.3510] 
  
  def get_gfs_processed_data1():
      start = pd.Timestamp(datetime.date.today(), tz=time_zone) #used for testing last week
      end = start + pd.Timedelta(days=6)
      gfs = GFS(resolution='quarter')
      #get processed data for lat/long point
      forecasted_data = gfs.get_processed_data(barnwell_list[1], barnwell_list[2], start, end)
      forecasted_data.to_excel(writer, sheet_name='Sheet1')
  
  
  get_gfs_processed_data1()
  </code></pre>