Version: 1.10.92 (using 4.1.85 (KDE 4.1.85 (KDE 4.2 Beta2)), Kubuntu packages) Compiler: cc OS: Linux (x86_64) release 2.6.27-9-generic If you chose the aggregation "Activity by Date, Flat", the group headers for everything older than a week will use the US date-format MM/DD/YY, at least on an English system. Instead it should use either the system settings (YYYY-MM-DD here) or the settings from Appearance->Message List-> Date Format.
also in 1.11.0 kde 4.2.0
*** This bug has been marked as a duplicate of bug 196108 ***