Merge pull request #2651 from httpwg/mnot/2622

Require supported Date ranges

draft-ietf-httpbis-sfbis.md

@@ -485,14 +485,17 @@ Note that in Dictionary ({{dictionary}}) and Parameter ({{param}}) values, Boole
 
 Date values can be conveyed in Structured Fields.
 
-Dates have a data model that is similar to Integers, representing a (possibly negative) delta in seconds from January 1, 1970 00:00:00 UTC, excluding leap seconds.
+Dates have a data model that is similar to Integers, representing a (possibly negative) delta in seconds from 1970-01-01T00:00:00Z, excluding leap seconds.
 
 For example:
 
 ~~~ http-message-new
 Example-Date: @1659578233
 ~~~
 
+Parsers MUST support Dates whose values include all days in years 1 to 9999 (i.e., -62,135,596,800 to 253,402,214,400 delta seconds from 1970-01-01T00:00:00Z).
+
+
 ### Display Strings {#displaystring}
 
 Display Strings are similar to Strings, in that they consist of zero or more characters, but they allow Unicode content, unlike Strings.