DateTime issues in django xlsxwriter

I am trying to create an export to excel in my django view like this:

def export_myreport(request, sd, ed):
    from xlsxwriter.workbook import Workbook
    import cStringIO as StringIO
    from django.utils.encoding import smart_str

    # create a workbook in memory
    output = StringIO.StringIO()

    wb = Workbook(output)

    bg = wb.add_format({'bg_color': '#9CB640', 'font_color': 'black'})
    bg2 = wb.add_format({'bg_color': '#FFFFFF', 'font_color': 'black'})

    ws = wb.add_worksheet('My Report')

    row_num = 0

    summary = MyModel.objects.filter(time__range = (sd, ed)).select_related()

    row_num += 2
    row = [
        smart_str(u"Time"),
        smart_str(u"Item"),
        smart_str(u"User")
    ]
    for col_num in xrange(len(row)):
        ws.write(row_num, col_num, row[col_num], bg)

    for s in summary:
        row_num += 1
        row2 = [
            s.time,
            s.model_name,
            s.user.first_name
        ]
        for col_num in xrange(len(row2)):
            ws.write(row_num, col_num, row2[col_num], bg2)

    wb.close()

    output.seek(0)
    response = HttpResponse(output.read(), content_type="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet")
    response['Content-Disposition'] = "attachment; filename=myreport.xlsx"

    return response

      

        
        
        
      

    

But I am getting some problems with DateTime formatting! Perhaps there is something I am missing here?

Here is the error I am getting:

TypeError at /myapp/export_myreport/2015-05-01/2015-05-19
can't subtract offset-naive and offset-aware datetimes

      

        
        
        
      

    

EDIT:

This is how I call url in my html:

<a href="export_myreport/{{begindate}}/{{enddate}}" class="btn btn-default pull-right" role="button">Export to XLSX</a>

      

        
        
        
      

    

Here {{begindate}}

and {{enddate}}

are variable angular.