unix date format converting HKT or JST to EST timezone - date

Question

While converting the date to +%-m/%-d/%Y using date format in unix, I'm getting dates converted to timezones. HKT or JST timezones to EST, I want the date as is to be converted as mm/dd/yy without this timezone conversion
Example:
$ date -u '--d=Sun Jan 25 08:39:12 JST 2015' +%-m/%-d/%Y
1/24/2015
I also tried with -u -d options
$ date -u -d 'Sun Jan 25 08:39:12 JST 2015' +%-m/%-d/%Y
1/24/2015
Can someone please help me with the solution.

Answer 1

To change the output timezone, you could set TZ envvar:
$ TZ=EST date -d 'Sun Jan 25 08:39:12 JST 2015'
Sat Jan 24 18:39:12 EST 2015
$ TZ=JST date -d 'Sun Jan 25 08:39:12 JST 2015'
Sun Jan 25 08:39:12 JST 2015
To ignore the input timezone or to detect it automatically, a Python script could be used:
#!/usr/bin/env python
"""Change date/time format.
Usage: $ {prog} <input-date-time> <output-format>
Example: $ ./change-date-format 'Sun Jan 25 08:39:12 JST 2015' %-m/%-d/%Y
Output: 1/25/2015
"""
import sys
from dateutil.parser import parse # apt-get install python-dateutil
try:
date_string, date_format = sys.argv[1:]
except ValueError:
sys.exit(__doc__.format(prog=sys.argv[0])) # print usage info
else:
datetime_object = parse(date_string)
print(datetime_object.strftime(date_format))