I will say when the BTVS bits take place, as it skips around a lot. And as for Supernatural, it takes place in the 5 year gap between 15.19 and 15.20! One day, a ghost attacks Sunnydale- and the ghost is vanquished by the Scoobies, with help, of course. A few months later, a demon attacks. And is soon backed up by an evil angel. What are they planning to do with The Empty? And can they be stopped?