Find any gaps in dates across 3 years

Find any gaps in dates across 3 years

I'm building an application form for new employees, and I'd like them to input their previous employers and dates over the last 3 years. 

What would be the easiest way to validate that every day over the last 3 years is accounted for, and that there are no gaps of over 30 days?

I imagine this can get cumbersome so if anyone's got any tips, I'm all ears. 

Thanks!
Brian