It was noted on gnus.general that it's weird to have the Date header as
part of the default value of `message-draft-headers'. Having it in there
means that a Date header is generated (and fixed) when a message is
first saved or delayed, not when it is sent. In the case of delayed
messages, in particular, it's weird that the eventually-sent message can
have a Date header days or weeks in the past.

Is there any interest in changing the default value?

Eric