[LEAPSECS] email headers

[Zefram]

According to RFC 5322 (and its predecessor RFC 2822), the Date: header
that I'm putting on this message is valid:

	Date: Sun, 01 Jul 2012 00:59:60 +0100

I wonder how many MUAs will be unable to date-sort it.  The header
syntax is specified rather loosely: the BNF allows "99:99:99" as a
time-of-day, it being merely semantically forbidden, and the usage of
":60" is only weakly implied to be limited to leap seconds.  This is
typical of email header definitions, particularly the older ones, and
thus the tradition is for email headers to be handled very forgivingly.
So I presume this message will pass through the mail transport system
unhindered, and be readable in anyone's MUA, even where software thinks
the header is bogus.  So I think date sorting is all that's likely to
go wrong with this message.

-zefram