Usage: ./dtconvert.php <timestamp> <to-timezone>

dtconvert.php

#!/usr/bin/env php
<?php /* vim: set expandtab tabstop=4 shiftwidth=4 softtabstop=4: */

if (php_sapi_name() !== "cli") {
    http_response_code(500);
    exit("Must be ran by php-cli");
}

if ($argc < 3) {
    exit(
        "Usage: " . $argv[0] . " <timestamp> <to-timezone>" . PHP_EOL .
        PHP_EOL .
        "  timestamp    Any timestamp representation that is valid" . PHP_EOL .
        "               with the strtotime() function. Note that" . PHP_EOL .
        "               timestamps without a timezone are assumed" . PHP_EOL .
        "               to be in UTC, override this by appending" . PHP_EOL .
        "               a timezone to the timestamp." . PHP_EOL .
        "  to-timezone  The timezone to convert timestamp to, see:" . PHP_EOL .
        "               <http://php.net/manual/en/timezones.php>" . PHP_EOL .
        PHP_EOL
    );
}

$timestamp = $argv[1];
$target    = $argv[2];

$tz        = new DateTimeZone("UTC");
$timestamp = new DateTime($timestamp, $tz);
$target    = new DateTimeZone($target);

echo $timestamp->setTimezone($target)->format("c") . PHP_EOL;