This text file consists of three Python files. The first is a very slightly adapted code fount on github, which listens for new blocks from the blockchain.info websocket API. Change the file output location to whatever you prefer, and let it run as long as you want to collect as many blocks as you need. The next two files must be run in sequence (you can leave the first running if you wish). File 2 takes the output of the listener routine and turns it into CSV timestamps. File 3 takes that and turns it into a CSV of time-between-blocks. This output can then be analyzed in whatever way you wish.

# FILE 1: bitcoin_listener
# -*- coding: utf-8 -*-
# by fcicq <fcicq@fcicq.net>, 2013.4.7, GPLv2
# Tornado 3.0 is required.
"""
Original code at: https://gist.github.com/fcicq/5328876/
Extremely minor modifications by Matt Springer
"""

from tornado.websocket import websocket_connect, WebSocketClientConnection
from tornado.ioloop import IOLoop
from datetime import timedelta
import time

#echo_uri = 'ws://echo.websocket.org'
echo_uri = 'ws://ws.blockchain.info/inv'
PING_TIMEOUT = 15
class myws():
  conn = None
  keepalive = None
  def __init__(self, uri):
    self.uri = uri
    self.doconn()
  def doconn(self):
    w = websocket_connect(self.uri)
    w.add_done_callback(self.wsconnection_cb)
  def dokeepalive(self):
    stream = self.conn.protocol.stream
    if not stream.closed():
      self.keepalive = stream.io_loop.add_timeout(timedelta(seconds=PING_TIMEOUT), self.dokeepalive)
      self.conn.protocol.write_ping("")
    else:
      self.keepalive = None # should never happen
  def wsconnection_cb(self, conn):
    self.conn = conn.result()
    self.conn.on_message = self.message
    self.conn.write_message('{"op":"ping_block"}')
    self.conn.write_message('{"op":"blocks_sub"}')
#    self.conn.write_message('{"op":"unconfirmed_sub"}')
    self.keepalive = IOLoop.instance().add_timeout(timedelta(seconds=PING_TIMEOUT), self.dokeepalive)
  def message(self, message):
    if message is not None:
      output = str(message) + str(time.time())  
      print(output)
      with open('c:\users\matt\desktop\log.txt', 'a') as the_file:
          the_file.write(output)
          the_file.write('\n')
          the_file.close()
    else:
      self.close()
  def close(self):
    print('conn closed')
    if self.keepalive is not None:
      keepalive = self.keepalive
      self.keepalive = None
      IOLoop.instance().remove_timeout(keepalive)
    self.doconn()

import signal
def main():
  try:
    io_loop = IOLoop.instance()
    signal.signal(signal.SIGTERM, io_loop.stop)
    myws(echo_uri)
    IOLoop.instance().start()
  except KeyboardInterrupt:
    io_loop.stop()

if __name__ == '__main__':
  main()

# FILE 2: bitcoin_parser
# -*- coding: utf-8 -*-
"""
Coded by Matt Springer
This work is licensed under a Creative Commons Attribution 4.0 International License.
"""
from __future__ import print_function
import re

def getHeight(string):
    '''Regex which matches the 6 digits following "height" in the received block'''
    regex = re.compile("(?<=\"height\":)[0-9]{6}")
    result = regex.findall(string)
    return int(result[0])

def getReportedTime(string):
    '''Extacts the number after the first "time" in the received block'''
    regex = re.compile("(?<=\"time\":)[0-9]{10}")
    result = regex.findall(string)
    return int(result[0])
    
def getBlockchainTime(string):
    '''Extacts the number after the second "time" in the received block '''
    regex = re.compile("(?<=\"time\":)[0-9]{10}")
    result = regex.findall(string)
    return int(result[1])
    
def getMyTime(string):
    '''Extacts the number after the three}}}, which is the local machine timestamp I appended in bitcoin_listener'''
    regex = re.compile("(?<=\}\}\})[0-9]{10}")
    result = regex.findall(string)
    return int(result[0])


def main():
    '''prints comma-separated data in the form [block height, internal block timestamp, blockchain.info timestame, local machine timestamp] I only use the local timestamp'''
    f = open('c:\users\matt\desktop\log.txt', 'r')
    g = open('c:\users\matt\desktop\processed.txt', 'w')
    counter = 0    
    for line in f:
        print(str(getHeight(line)) + ',' + str(getReportedTime(line)) + ',' + str(getBlockchainTime(line)) + ',' + str(getMyTime(line)))
        g.write(str(getHeight(line)) + ',' + str(getReportedTime(line)) + ',' + str(getBlockchainTime(line)) + ',' + str(getMyTime(line)) +'\n')
        counter += 1
    f.close()
    g.close()
    print(counter)

main()

# FILE 3: bitcoin_parser
# -*- coding: utf-8 -*-
"""
Coded by Matt Springer
This work is licensed under a Creative Commons Attribution 4.0 International License.
"""
from __future__ import print_function
import csv

def main():
    indexArray = []
    timeArray = []    
    with open('c:\users\matt\desktop\processed.txt', 'rb') as csvfile:
        reader = csv.reader(csvfile, delimiter=',')
        for row in reader:
            indexArray.append(int(row[0]))            
            timeArray.append(int(row[3]))
        
    for index in range(len(timeArray)-1):
        '''the "if" statement rejects non-consecutive blocks'''
        if(indexArray[index + 1] == indexArray[index] + 1):
            print(indexArray[index], end=',')            
            print(timeArray[index + 1] - timeArray[index])
main()