See http://purl.org/tcl/home/man/tcl8.5/TclCmd/clock.htm
In 8.5, the old (up to 8.4) [clock scan] command is deprecated in favour of the new [clock scan -format].
This is covered by TIP #173 [L1 ], and I understand the reasons behind creating the new version, but I think it would be a great pity to lose a great usability aid for applications that use dates - an easy way of letting the user type in "yesterday" or "last week". I may be missing something, but I can't see any way to deal with this in the new version.
I guess what I am really saying is, deprecate it if you like, but don't ever take the old code out.