Not to beat a dead horse ( http://arclanguage.com/item?id=3351 ), but what platform are you developing Arc on? 'date -u -r' doesn't work on Linux or OS X, so we have to keep patching arc.arc with each new release.
edit: I looked at the patch more carefully and it looks like BSD accepts -r, so the next question is, would you mind adding some platform dependent conditionals?
My bad. In my haste, I simply ssh'd to my Mac and issued 'date -u -r' and didn't take the time to see that it was simply complaining about the fact that I didn't provide an argument for -r. So, I guess it's a problem for Linux, and not for OSX.