display date header in local time in mutt

mail_filter.py

#!/usr/bin/env python

# Save this in a file somewhere
# In your mutt config add the following line
# set display_filter="/PATH/TO/THIS/PYTHON/FILE"

import sys
import re
import os

message = sys.stdin.read()
in_headers = True

for line in message.split('\n'):
    if line == '':
        in_headers = False

    match = re.match(r'^Date: (.+$)', line)
    if in_headers and match:
        date_string = match.group(1)
        converted_date = os.popen('date -d "{}"'.format(date_string)).read()
        print('Date: {}'.format(converted_date.strip()))
    else:
        print(line)

i made a python 3.3 version at http://unix.stackexchange.com/a/229619/14305

you are not escaping the shell argument properly.