Package: libicu63 Version: 63.1-6 I have encountered a bug with timezones in Plasmashell's Digital Clock widget, which I have reported upstream, but the upstream KDE maintainer pointed out that it's actually a bug in the ICU and asked to file it against Debian, so here I am.
You can find all the necessary information in the original bug report filed against Plasmashell at https://web.archive.org/web/20190317151311/https://bugs.kde.org/show_bug.cgi?id=405288 I could copy it over if you prefer that.