Adding date

See pubDate definition in [RSS 2.0 Specification](http://validator.w3.org/feed/docs/rss2.html):

All date-times in RSS conform to the [Date and Time Specification of RFC 822](http://www.w3.org/Protocols/rfc822/#z28), with the exception that the year may be expressed with two characters or four characters (four preferred).

Here are examples of valid RFC822 date-times:

```
Wed, 02 Oct 2002 08:00:00 EST

Wed, 02 Oct 2002 13:00:00 GMT

Wed, 02 Oct 2002 15:00:00 +0200
```

Read the RSS generation entry point and inspect how feed items are assembled; the payload does not name a file or test. Compare the output with the RSS 2.0 pubDate definition and RFC 822 examples, then verify that generated feeds contain a valid pubDate value.

Rédigé par le modèle d'indexation à partir du texte de l'issue.