EasyTimeline replaces all characters above 255 and even some in that range with
ASCII approximations or underscores. This breaks almost all national diactrics
for latin alphabet and all of other character sets.
One possible solution requires recompiling ploticus with freetype support and
changing a few lines in EasyTimeline.pl and Timeline.php, and making an unicode
ttf font available to the ploticus. I'll put diffs into attachments.