I have seen that on sendmail 5.65 it seems that the year in the date field is writen with 4 digits :
ex :
in 5.61 :
Tue, 18 Aug 92 12:08:02 +0200
in 5.65 :
Tue, 18 Aug 1992 12:08:02 +0200
I presume this is not a hazard : year 2000 is comming and it is probably the reason of that change.
But this causes me a problem on a gateway which is not able to manage that format. And I would like to know if there an RFC or some think concerning this before submitting the problem to the gateway's programmer.