Carry time estimates through when syncing with OSX calendar

I’ve just started using the OSX Calendar synch feature. Tasks with due dates/times carry through from Omnifocus to Calendar at the correct date and time. BUT, estimated time doesn’t carry through for some reason. The result is omnifocus-generated events in calendar with zero time. Have you seen this problem? Or not seen it? Is it just something in my synch setup? Or is it just something I have to live with for now? Thanks