Vistime using years not dates

Question

I'm creating a timeline using vistime and there are two problems.

1. It is always trying to show the graph with dates from 01/01/1970 rather than the years I have put in the dataset. How do I do it has number

2. As it is a timeline of prehistoric events I need it going from big to small rather than small to big. How do I do this?

Data set

Code

    vistime(Stegosauridae_Info, 
    col.event = "Genus", 
    title = "Stegosauridae",
    optimize_y = FALSE,
    linewidth = 25)