http://www.tcl.tk/man/tcl8.4/TclCmd/time.htm
In a different use of the word time, LV asks "Has anyone written a time chooser similar to the date chooser widgets written elsewhere on the Wiki?"
Larry refers to A little date chooser and An i15d date chooser. You can measure the runtime of a lengthy script with the following pattern:
Tcl syntax help - Arts and crafts of Tcl-Tk programming - Category Command