Vacations days will not show in my gant chart>>?

I have added vacation days for all people involved in my project but when i open my gant chart it does not show. I can still plan work in those days. How can I make sure those vacations days will block any work in my gant chart? Thnx!

Vacation days are just colored bars on resource chart. They do not affect tasks schedules in any way, sorry. See https://github.com/bardsoftware/ganttproject/issues/18