You can use the =DATEDIF to calculate a person's age. For example, the formula below will calculate the age of a person as of the current date, where DOB is the person's date of birth.
Formula: =DATEDIF(Date1, Date2, Interval)
="Hi " & "Your name" & " your age is " & DATEDIF(YourDOB,TODAY(),"Y") & " Year " & DATEDIF(YourDOB,TODAY(),"ym") & " Months and " & DATEDIF(YourDOB,TODAY(),"md") & " Day's"
Note : Make sure that you wright “your name” and “your DOB” correct or pass
For example:-
="Hi " & B4 & " your age is " & DATEDIF(C4,TODAY(),"Y") & " Year " & DATEDIF(C4,TODAY(),"ym") & " Months and " & DATEDIF(C4,TODAY(),"md") & " Day's"