Here's an alternate version which uses the underlying mzscheme date-handling library; it's less "bootstrapped", but also supports formatting of arbitrary timestamps under Linux.
(Feel free to ignore the 'os-name' and 'chomp' functions added to arc.arc; they are obviously from an earlier variant of the function which used the same approach as @starc.)
Agreed, though what I'd really like is a full time/date stack built in Arc...using the MzScheme primitives is pretty ugly for a supposedly "bootstrapped" language.
There are enough other areas where Arc is coupled to the underlying Scheme runtime, though, that it's probably not worth worrying about at this point.
