How many years from start date formula

Thanks for replying

I don't seem to have that formula when I press =? I only have DATE and DATEVALUE?

I have attached an example of what I have done so far. What I am trying to do is summarise the data before putting it into a table but as you can see I'm having a bit of trouble.

When an employee has worked less than a year its not sure what range to put it in. How can I get round this? I think I may need to put some dates in months?