Note that you cannot calculate the age of a person in years when you know their age in days. So your function will need to work on both dates and not on their difference:
julia> function age(dob, date)
age = Dates.year(date)- Dates.year(dob) -1
if Dates.month(date)>Dates.month(dob) || (Dates.month(date)==Dates.month(dob) && Dates.day(date)>=Dates.day(dob))
age += 1
end
return age
end
PS: have another read on how to quote your code: PSA: how to quote code with backticks