utc_to_timezone converts a time string from a timezone to another

utc_to_timezone.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
import sys
import errno


def error(msg):
    print >> sys.stderr, msg


def info(msg):
    print >> sys.stdout, msg


try:
    import pytz
except ImportError:
    error("pytz not installed. please install pytz (pip install pytz).")
    sys.exit(status=errno.ENOPKG)

from argparse import ArgumentParser, ArgumentError
from datetime import datetime

FORMATS = ['%Y-%m-%d %H:%M', '%Y/%m/%d %H:%M', '%H:%M']


def discover_datetime(timestr):

    for _format in FORMATS:
        try:
            d = datetime.strptime(timestr, _format)
        except ValueError:
            pass
        else:
            # if match format does not contains date, add to it now()
            if '%Y' not in _format:
                n = datetime.utcnow()
                return datetime(n.year, n.month, n.day, d.hour, d.minute)
            return d
    error("Can't discover format. Use one of formats %s." % ', '.join(FORMATS))
    sys.exit(status=errno.EINVAL)


def discover_timezone(zone):
    try:
        return pytz.timezone(zone)
    except pytz.UnknownTimeZoneError:
        error("Unknow timezone %s. Use know timezones please." % zone)


def convert_to_timezone(timestr, from_zone, to_zone):

    d = discover_datetime(timestr)

    try:
        from_zone = pytz.timezone(from_zone)
    except pytz.UnknownTimeZoneError:
        error("Unknow 'from' timezone %s. Use know timezones please." %
              from_zone)
        sys.exit(status=errno.EINVAL)

    try:
        to_zone = pytz.timezone(to_zone)
    except pytz.UnknownTimeZoneError:
        error("Unknow 'to' timezone %s. Use know timezones please." % to_zone)
        sys.exit(status=errno.EINVAL)

    d = from_zone.localize(d)

    info("%s (%s) => %s (%s)" % (
         d.strftime("%Y-%m-%d %H:%M"), from_zone,
         d.astimezone(to_zone).strftime("%Y-%m-%d %H:%M"), to_zone))

parser = ArgumentParser