Although you can use the

{{ game.gameDate|date('Y-m-d') }}

approach, keep in mind that this version does not honor the user locale, which should not be a problem with a site used by only users of one nationality. International users should display the game date totally different, like extending the \DateTime class, and adding a __toString() method to it that checks the locale and acts accordingly.

Edit:

As pointed out by @Nic in a comment, if you use the Intl extension of Twig, you will have a localizeddate filter available, which shows the date in the user’s locale. This way you can drop my previous idea of extending \DateTime.

You can use date filter:

{{ game.gameDate|date("m/d/Y") }}

It depends on the format you want the date to be shown as.

Static date format

If you want to display a static format, which is the same for all locales (for instance ISO 8601 for an Atom feed), you should use Twig's date filter:

{{ game.gameDate|date('Y-m-d\\TH:i:sP') }}

Which will allways return a datetime in the following format:

2014-05-02T08:55:41Z

The format strings accepted by the date filter are the same as you would use for PHP's date() function. (the only difference is that, as far as I know, you can't use the predefined constants which can be used in the PHP date() function)

Localized dates (and times)

However, since you want to render it in the browser, you'll likely want to show it in a human-readable format, localised for the user's language and location. Instead of doing the localization yourself, you can use the Intl Extension for this (which makes use of PHP's IntlDateFormatter). It provides a filter localizeddate which will output the date and time using a localized format.

localizeddate( date_format, time_format [, locale ] )

Arguments for localizeddate:

• date_format: One of the format strings (see below)
• time_format: One of the format strings (see below)
• locale: (optional) Use this to override the configured locale. Leave this argument out to use the default locale, which can be configured in Symfony's configuration.

(there are more, see the docs for the complete list of possible arguments)

For date_format and time_format you can use one of the following strings:

• 'none' if you don't want to include this element
• 'short' for the most abbreviated style (12/13/52 or 3:30pm in an English locale)
• 'medium' for the medium style (Jan 12, 1952 in an English locale)
• 'long' for the long style (January 12, 1952 or 3:30:32pm in an English locale)
• 'full' for the completely specified style (Tuesday, April 12, 1952 AD or 3:30:42pm PST in an English locale)

Example

So, for instance, if you want to display the date in a format equivalent to February 6, 2014 at 10:52 AM, use the following line in your Twig template:

{{ game.gameDate|localizeddate('long', 'short') }}

However, if you use a different locale, the result will be localized for that locale:

• 6 februari 2014 10:52 for the nl locale;
• 6 février 2014 10:52 for the fr locale;
• 6. Februar 2014 10:52 for the de locale;etc.

As you can see, localizeddate does not only translate the month names but also uses the local notations. The English notation puts the date after the month, where Dutch, French and German notations put it before the month. English and German month names start with an uppercase letter, whereas Dutch and French month names are lowercase. And German dates have a dot appended.

Installation / setting the locale

Installation instructions for the Intl extension can be found in this seperate answer.