RFC 2822 is already obsolete, and this part was somewhat fixed in RFC 5322.  See Section 3.3 of that document, in that those old zone names are marked as obsolete, but allowed.  Pete can say more if he wants.

Eliot

On Thu, 2 Mar 2023 at 17:45, Paul Eggert via tz <tz@iana.org> wrote:

Whether the adjusted time in (say) New York would be abbreviated "EST"
or "AST" or "EDT" is up to common practice.

[…]

At some point "EST" might become the
best of the alternatives.

Worth considering that, if "EST" were to become standard for -04, it would require modifications to supported, but obsoleted, formats in RFC 2822 §4.3, which state:

EDT is semantically equivalent to -0400
EST is semantically equivalent to -0500
CDT is semantically equivalent to -0500
CST is semantically equivalent to -0600
MDT is semantically equivalent to -0600
MST is semantically equivalent to -0700
PDT is semantically equivalent to -0700

PST is semantically equivalent to -0800 

--
Tim Parenti