Currently with Gtk3 (even with Adwaita, which is famous for being a bit inflated) the calendar style of the clock plugin looks too condensed (it's actually partly GtkCalendar's fault, it seems to be a fairly unmaintained widget). This issue is also tracked upstream for now, maybe we'll integrate some changes in the panel (where needed) * https://bugzilla.gnome.org/show_bug.cgi?id=780327 * https://bugzilla.gnome.org/show_bug.cgi?id=780334 * https://bugzilla.gnome.org/show_bug.cgi?id=780328 We could also consider doing our own widget for this, which would probably result in a fork of GtkCalendar...
Forking is probably best (after talking to Gtk devs). Best place for that is probably libxfce4ui.