I'm afraid you're all barking up the wrong tree.
Yes, a posting time needs a timezone. Or it is useless. So said RFC1036[0]. The text in the successor RFC5536[1] basically enforces it by quoting RFC5322[2].
Postings here come without, with, in a mess. I am fully aware that trying to get people to swap buggy clients is futile. Perhaps they can be convinced that some config changes in reader view are useful:
Set your clients to References: threading, and move on. It was already suggested upthread.
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MN-1334-RIPE SA0XLR +46 705 989668 I just had a NOSE JOB!!
[0] This is chapter and verse on correct format, from RFC1036:2.1.2. Date
The "Date" line (formerly "Posted") is the date that the message was originally posted to the network. Its format must be acceptable both in RFC-822 and to the getdate(3) routine that is provided with the Usenet software. This date remains unchanged as the message is propagated throughout the network. One format that is acceptable to both is:
Wdy, DD Mon YY HH:MM:SS TIMEZONE
Several examples of valid dates appear in the sample message above. Note in particular that ctime(3) format:
Wdy Mon DD HH:MM:SS YYYY
is not acceptable because it is not a valid RFC-822 date. However, since older software still generates this format, news implementations are encouraged to accept this format and translate it into an acceptable format.
There is no hope of having a complete list of timezones. Universal Time (GMT), the North American timezones (PST, PDT, MST, MDT, CST, CDT, EST, EDT) and the +/-hhmm offset specifed in RFC-822 should be supported. It is recommended that times in message headers be transmitted in GMT and displayed in the local time zone.
[1] This is 5536:Murchison, et al. Standards Track [Page 10] RFC 5536 Netnews Article Format November 2009
3.1.1. DateThe Date header field is the same as that specified in Sections 3.3 and 3.6.1 of [RFC5322], with the added restrictions detailed above in Section 2.2. However, the use of "GMT" as a time zone (part of ), although deprecated, is widespread in Netnews articles today. Therefore, agents MUST accept constructs that use the "GMT" zone.
orig-date = "Date:" SP date-time CRLF
NOTE: This specification does not change [RFC5322], which says that agents MUST NOT generate constructs that include any zone names defined by .
Software that accepts dates with unknown timezones SHOULD treat such timezones as equivalent to "-0000" when comparing dates, as specified in Section 4.3 of [RFC5322].
Also note that these requirements apply wherever is used, including Injection-Date and Expires (Sections 3.2.7 and 3.2.5, respectively).
[2]