s-o-1036 June 1994

6.2. Expires

The  Expires  header  content specifies a date and time when
the article is deemed to be no longer useful and  should  be
removed ("expired"):

     Expires-content = Date-content

The  content syntax is the same as that of the Date content.
In the absence of Expires, the default  is  decided  by  the
administrators  of  each  host  the article reaches, who MAY
also restrict the extent to which the Expires header is hon-
ored.

The Expires header has two main applications: removing arti-
cles whose utility ends on  a  specific  date  (e.g.,  event
announcements which can be removed once the day of the event
is past) and preserving articles expected to be of prolonged
usefulness  (e.g.,  information  aimed  at  new readers of a
newsgroup).  The latter  application  is  sometimes  abused.
Since individual hosts have local policies for expiration of
news (depending on  available  disk  space,  for  instance),
posters  SHOULD  not  provide  Expires  headers for articles
unless there is a natural expiration  date  associated  with
the  topic.   Posting  agents  MUST  not  provide  a default
Expires header.  Leave it out and allow local policies to be
used unless there is a good reason not to.  Expiry dates are
properly the decision  of  individual  host  administrators;
posters  and  moderators  SHOULD  set only expiry dates that
most administrators would agree with.

     NOTE: A poster preparing an Expires header for  an
     article  whose  utility  ends  on  a  specific day
     should typically  specify  the  NEXT  day  as  the
     expiry  date.   A  meeting  on July 7th remains of
     interest on the 7th.

--- ../rfc1036/Expires.out          December 1987
+++ ../s-o-1036/Expires.out          June 1994
@@ -1,17 +1,37 @@
-2.2.4.  Expires
+6.2. Expires
 
-    This line, if present, is in a legal USENET date format.  It
-    specifies a suggested expiration date for the message.  If not
-    present, the local default expiration date is used.  This field is
-    intended to be used to clean up messages with a limited usefulness,
-    or to keep important messages around for longer than usual.  For
-    example, a message announcing an upcoming seminar could have an
-    expiration date the day after the seminar, since the message is not
-    useful after the seminar is over.  Since local hosts have local
-    policies for expiration of news (depending on available disk space,
-    for instance), users are discouraged from providing expiration dates
-    for messages unless there is a natural expiration date associated
-    with the topic.  System software should almost never provide a
-    default "Expires" line.  Leave it out and allow local policies to be
-    used unless there is a good reason not to.
+The  Expires  header  content specifies a date and time when
+the article is deemed to be no longer useful and  should  be
+removed ("expired"):
+
+     Expires-content = Date-content
+
+The  content syntax is the same as that of the Date content.
+In the absence of Expires, the default  is  decided  by  the
+administrators  of  each  host  the article reaches, who MAY
+also restrict the extent to which the Expires header is hon-
+ored.
+
+The Expires header has two main applications: removing arti-
+cles whose utility ends on  a  specific  date  (e.g.,  event
+announcements which can be removed once the day of the event
+is past) and preserving articles expected to be of prolonged
+usefulness  (e.g.,  information  aimed  at  new readers of a
+newsgroup).  The latter  application  is  sometimes  abused.
+Since individual hosts have local policies for expiration of
+news (depending on  available  disk  space,  for  instance),
+posters  SHOULD  not  provide  Expires  headers for articles
+unless there is a natural expiration  date  associated  with
+the  topic.   Posting  agents  MUST  not  provide  a default
+Expires header.  Leave it out and allow local policies to be
+used unless there is a good reason not to.  Expiry dates are
+properly the decision  of  individual  host  administrators;
+posters  and  moderators  SHOULD  set only expiry dates that
+most administrators would agree with.
+
+     NOTE: A poster preparing an Expires header for  an
+     article  whose  utility  ends  on  a  specific day
+     should typically  specify  the  NEXT  day  as  the
+     expiry  date.   A  meeting  on July 7th remains of
+     interest on the 7th.