code: def get_modified_date(parsed, raw):
  	'Return best possible guess to post modification timestamp.'
  	if parsed: return feedparser_ts(parsed)
  	if not raw: return None
  
  	# Parse weird timestamps that feedparser can't handle, e.g.: July 30, 2013
  	ts, val = None, raw.replace('_', ' ')
  	if not ts:
  		# coreutils' "date" parses virtually everything, but is more expensive to use
  		from subprocess import Popen, PIPE
  		with open(os.devnull, 'w') as devnull:
  			proc = Popen(['date', '+%s', '-d', val], stdout=PIPE, stderr=devnull)
  			val = proc.stdout.read()
  			if not proc.wait():
  				ts = datetime.fromtimestamp(int(val.strip()), tz=timezone.utc)
  	if ts: return ts
  	raise ValueError('Unrecognized raw value format: {0!r}'.format(val)f get_modified_date(parsed, raw):
  	'Return best possible guess to post modification timestamp.'
  	if parsed: return feedparser_ts(parsed)
  	if not raw: return None
  
  	# Parse weird timestamps that feedparser can't handle, e.g.: July 30, 2013
  	ts, val = None, raw.replace('_', ' ')
  	if not ts:
  		# coreutils' "date" parses virtually everything, but is more expensive to use
  		from subprocess import Popen, PIPE
  		with open(os.devnull, 'w') as devnull:
  			proc = Popen(['date', '+%s', '-d', val], stdout=PIPE, stderr=devnull)
  			val = proc.stdout.read()
  			if not proc.wait():
  				ts = datetime.fromtimestamp(int(val.strip()), tz=timezone.utc)
  	if ts: return ts
  	raise ValueError('Unrecognized raw value format: {0!r}'.format(val))
docs: Return best possible guess to post modification timestamp.