Comment # 1 on bug 55238 from Patrick Ohly

(In reply to comment #0)
> Timezone for DUE in allday events is unhandled in calendar.xml script (
> src/syncevo/configs/scripting/11calendar.xml )
> 
> > if (ITEMDATATYPE()=="vCalendar10" && ALLDAYCOUNT(DUE,DUE,TRUE,TRUE)>0) {
> >     DUE = DATEONLY(DUE);
> > }
> 
> should probably have:
> >     DUE = CONVERTTOUSERZONE(DUE);
> before DUE = DATEONLY(DUE);

Looks reasonable. Does it fix the problem for you?