Leave it to Google to choose a format not even in the RFC.  I think we should also file a bug with them for not conforming.  Should we also support the obsolete RFC850 while we are at it? RFC6265 says the following:

HTTP/1.1 clients and servers that parse the date value MUST accept
   all three formats (for compatibility with HTTP/1.0), though they MUST
   only generate the RFC 1123 format for representing HTTP-date values
   in header fields.

Java is doing the following:
It passes the entire value of a Set-Cookie header to LiteCore.  E.g., from the example above:

Then, to any subsequent request, sent before the connection is completely open, it adds all of the cookies that it gets from LiteCore. It expects them in the format:

... or from the above example:

Note that everything except the name and the value have been truncated.

My conclusion is that Java is doing this correctly: It gives Lite Core the entire cookie and asks it for cookies before sending requests. As long Lite Core gives Java the correct cookies, Java will pass them on in the Open request.

Reference links :

https://www.rfc-editor.org/rfc/rfc6265#section-4.1.1

https://www.rfc-editor.org/rfc/rfc2616#section-3.3.1 (Referred by RFC 6265 as linked above)

The three formats from the above doc :

• Sun, 06 Nov 1994 08:49:37 GMT  ; RFC 822, updated by RFC 1123

• Sunday, 06-Nov-94 08:49:37 GMT ; RFC 850, obsoleted by RFC 1036

• Sun Nov  6 08:49:37 1994       ; ANSI C's asctime() format

GCLB Format :

Set-Cookie: GCLB=COWjp4rwlqauaQ; path=/; HttpOnly; expires=Tue, 22-Nov-2022 07:21:38 GMT

Mozilla doc (Seem to be inline with RFC 1123): 
https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Date

@Gabriel Terwesten Yes that's exactly right.  To fix this a more robust parsing method is needed.

From @Jim Borden's comment in the forum thread, I take that CBL already stores and sends cookies with subsequent requests. I think the GCBL cookies are getting dropped because CBL cannot parse the date format. That's in line with RFC 6265, which says that you should ignore cookies if the expiry date cannot be parsed. But the algorithm for parsing dates, described in that RFC, is more complex and allows for more format variations than what CBL implements.