InvoiceType.php

<?php

namespace SOTB\InvoiceBundle\Form\Type;

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolverInterface;

/**
 * Invoice form type.
 *
 * @author Matt Drollette <matt@drollette.com>
 */
class InvoiceType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('dateOfIssue', 'date', array(
                'data_timezone' => 'UTC',
                'user_timezone' => $options['user_timezone']
            ))
            ->add('terms', 'textarea', array(
                'required' => false
            ))
            ->add('visibleNotes', 'textarea', array(
                'required' => false
            ))
        ;
    }

    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver
            ->setDefaults(array(
                'data_class'        => 'SOTB\CoreBundle\Document\Invoice',
                'user_timezone'     => 'UTC'
            ));
    }

    public function getName()
    {
        return 'sotb_invoice_type';
    }
}

LocaleExtension.php

<?php

namespace SOTB\CoreBundle\Twig\Extension;

use Symfony\Component\DependencyInjection\ContainerInterface;

/**
 * @author Matt Drollette <matt@drollette.com>
 */
class LocaleExtension extends \Twig_Extension
{
    protected $container;
    protected $timezone;

    public function __construct(ContainerInterface $container)
    {
        $this->container = $container;
        $this->timezone = $this->container->get('session')->get('timezone', 'UTC');
    }

    public function getFunctions()
    {
        return array();
    }

    public function getFilters()
    {
        return array(
            'datetime' => new \Twig_Filter_Method($this, 'formatDatetime', array('is_safe' => array('html'))),
        );
    }

    public function formatDatetime($date, $timezone = null)
    {
        if (null === $timezone) {
            $timezone = $this->timezone;
        }

        if (!$date instanceof \DateTime) {
            if (ctype_digit((string) $date)) {
                $date = new \DateTime('@'.$date);
            } else {
                $date = new \DateTime($date);
            }
        }

        if (!$timezone instanceof \DateTimeZone) {
            $timezone = new \DateTimeZone($timezone);
        }

        $date->setTimezone($timezone);

        return $date;
    }

    public function getName()
    {
        return 'sotb_core_locale';
    }
}

LocaleListener.php

<?php

namespace SOTB\CoreBundle\EventListener;

/**
 * @author Matt Drollette <matt@drollette.com>
 */
class LocaleListener
{
    protected $container;

    public function __construct($container)
    {
        $this->container = $container;
    }

    public function onKernelRequest($request)
    {
        $locales = array();
        $request = $request->getRequest();

        if ($request) {
            $locales[] = $request->getLocale();
        }

        if ($request->server->has('HTTP_ACCEPT_LANGUAGE')) {
            $locales[] = \Locale::acceptFromHttp($request->server->get('HTTP_ACCEPT_LANGUAGE'));
        }

        foreach ($locales as $locale) {
            if (!empty($locale)) {
                if ($request) {
                    $request->setLocale($locale);
                }
                \Locale::setDefault($locale);
                break;
            }
        }
    }
}

SecurityListener.php

<?php

namespace SOTB\CoreBundle\EventListener;

use Symfony\Component\Security\Http\Event\InteractiveLoginEvent;
use Symfony\Component\Security\Core\SecurityContext;
use Symfony\Component\HttpFoundation\Session\Session;

/**
 * @author Matt Drollette <matt@drollette.com>
 */
class SecurityListener
{
    protected $security;
    protected $session;

    /**
     * Constructs a new instance of SecurityListener.
     *
     * @param SecurityContext $security   The security context
     * @param Session         $session    The session
     */
    public function __construct(SecurityContext $security, Session $session)
    {
        $this->security = $security;
        $this->session = $session;
    }

    /**
     * Invoked after a successful login.
     *
     * @param InteractiveLoginEvent $event The event
     */
    public function onSecurityInteractiveLogin(InteractiveLoginEvent $event)
    {
        $timezone = $this->security->getToken()->getUser()->getTimezone();
        if (empty($timezone)) {
            $timezone = 'UTC';
        }
        $this->session->set('timezone', $timezone);
    }
}

services-twig.xml

<service id="sotb_core.twig.extension" class="SOTB\CoreBundle\Twig\Extension\LocaleExtension">
    <tag name="twig.extension"/>
    <argument type="service" id="service_container"/>
</service>

services.xml

<service id="sotb_core.listener.login" class="SOTB\CoreBundle\EventListener\SecurityListener">
    <tag name="kernel.event_listener" event="security.interactive_login" method="onSecurityInteractiveLogin"/>
    <argument type="service" id="security.context"/>
    <argument type="service" id="session"/>
</service>