This is a request to open a project called cl-libtai.
Name: Lester Vecsey Description: Calendar and date functions for working with TAI, Temps Atomique International, time. License: LGPL Group members: None
This project would have many of the functions from the public domain C library libtai, at http://cr.yp.to/libtai.html
The real benefit here is the way that Lisp can easily handle large decimal and hexadecimal numbers, likely making this code rather compact when implemented. libtai usually packs time into an 8 or 16character hexadecimal sequence, so when checking output from other utilities and needing to convert or check a tai time these functions would make it real easy to do so from the REPL.
License would be LGPL to start with, and I do see from your FAQ there are concerns with that. In the future switching it to GPLv3 or LLGPL might be a good option worth considering. I'd be developing under CLISP, perhaps others will chime in with testing on other platforms and provide patches.