I happened upon a fairly robust date package for Tcl which does date parsing and has additional temporal functionality which comes together quite nicely. The original source of this package was http://web.uvic.ca/~erempel/tcl/DatePkg/DatePkg.html, but I have cleaned up some of the weird stuff (like nested, un-escaped quotes? ..quite funky/unnecessary), so here it is:
http://wi-fizzle.com/code/tcl/DatePkg/. Enjoy.