Passenger sometimes gets the date wrong when appending the http Date header to responses. This happens when the week-based year differs from the calendar year. It happens because it uses %G to print the year when it should be using %Y (see this commit: 15ed1d4).

Took me a few hours to track this down -- and it's probably affecting a large majority of the Rails apps that are using a Passenger server.

Hopefully getting the word out can save some folks a few hours of banging their heads on their desks.