Never had the joy(?) of doing a hardware design spec, but I once spent about a year of my life on the software design and spec for a major contract.
Even (especially!) standards as complex as the definitions of programming languages come with dates or version numbers. Fortran 66 is not Fortran 77 is not Fortran90 is not Fortran 95 is not Fortran2003 is not Fortran2008. Close, and there's probably a common subset in there somewhere, but they aren't the same.
Ditto for any other programming language with an ISO standard -- the year is part of the standard number. (Although curiously, C89 and C90 are the same language, because the 1989 ANSI C standard (X3.159-1989) was adopted as the ISO standard (ISO/IEC 9899:1990) in 1990.)
So yeah, if you're spec'ing something as part of a billion-dollar project, hardware or software, get the details nailed down. At the very least, stick in verbiage to the effect that "all standards named here-in, unless otherwise specified, shall refer to those current as of the date of this specification."