Ok, fixed most but not all issues. Reverting sscanf.c one revision solves this bug:
Pike v7.7 release 45 running Hilfe v3.5 (Incremental Pike Frontend)
Calendar.ISO.set_timezone("CET")->dwim_time("Tue Nov 19 07:04:03 NFT 2002")->format_time();
(1) Result: "2007-11-19 04:03:00"