new_contents: import pandas as pd
  import sys
  import datetime
  import calendar
  import argparse
  
  parser = argparse.ArgumentParser(description='Parse date column to unix.')
  parser.add_argument('--column', help='name of date column')
  parser.add_argument('--format', help='format of date values - see https://docs.python.org/2/library/datetime.html#strftime-and-strptime-behavior')
  args = parser.parse_args()
  
  # read csv from stdin into a dataframe
  df = pd.read_csv(sys.stdin, low_memory=False)
  
  def date_to_unix(d):
  	return calendar.timegm(datetime.datetime.strptime(d, args.format).utctimetuple())
  
  df[args.column] = df[args.column].map(date_to_unix)
  
  # output dataframe to stdout
  df.to_csv(sys.stdout, index=False)
  
subject: Create parse_date_to_unix.py