Calculate age (years and months) from two dates

Am trying get the (near accurate) age in years and months to populate in "Age on date of retirement" (Age1) from the date of birth (DOB1) and the date they retired (retireDate1). The only examples I've been able to find are for "today" dates. Can someone help with code? And I understand it works best with JavaScript but would FormCalc work also?

Dates are set as MM/DD/YYYY

Age field is num{z9}

Thanks in advance for your help!