You should use datetime.
>>> import datetime
>>> print(datetime.datetime.fromtimestamp(int("1385629728")).strftime('%Y-%m-%d %H:%M:%S'))
2013-11-28 14:38:48
>>> print int(datetime.datetime.strptime('2013-11-28 14:38:48', '%Y-%m-%d %H:%M:%S').strftime("%s"))
1385629728