Need to add 40 to the a numeric field value after a certain number of days pasts in another date field. Can anyone please help! Thanks!

First really appreciate your help! 

Next, good news is I realized the value that I should should be 120 should be 80... looked at the date again and it hasn't been 3 years. 

Based on your response above this field we just setup should actually be the renewal vacation time field.   So I've renamed that field and created a new field called available vacation time.  
How do I set that up so every year on their start date it adds the value on the renewal vacation time field? 

Hope that makes sense. 
Thanks again!