I haven't worked on it in forever, but advances in time travel have been made, if I poked at these advances I'm sure I could get it to be more of a sure thing. But as I have it now, it's more of a set year, but with all the different branches of time that flow through it's kind of a crap shoot, it's something you have to keep using until you find the right 'station'. And pray you don't run out of power before you do.