AGE

AGE(birthday, date_format)
Returns the age of someone given their birthday.

REMARKS
* If "birthday" is after todays date, then a negative value is returned.
* If "date_format" is left blank, then "UK" is used.
* If "dtBirthday" is not a valid date , then #VALUE! is returned.
* The formula to return a persons age in years.
* Alternatively you could use the following formula: =INT(YEARFRAC(TODAY(),"01/07/1977",1))

1 - What is the age of someone who has a birthday on "1/11/1977".
2 - What is the age of someone who has a birthday on "11/1/1977".

Public Function AGE( _ 
         ByVal dtBirthday As Date) _ 
         As Integer 

   If Int(dtBirthday) > 0 Then 
      Select Case Month(Date()) 
         Case Is < Month(dtBirthday) 
               AGE = Year(Date()) - Year(dtBirthday) - 1 
         Case Is = Month(dtBirthday) 
            If Day(Date) >= Day(dtBirthday) Then 
               AGE = Year(Date()) - Year(dtBirthday) 
            Else 
               AGE = Year(Date()) - Year(dtBirthday) - 1 
            End If 
         Case Is > Month(dtBirthday) 
            AGE = Year(Date()) - Year(dtBirthday) 
      End Select 
   Else 
      AGE = CVErr(xlErrNA) 
   End If 
End Function 

Function CalcAge(dteBirthdate As Date) As Long 

   Dim lngAge As Long 
    
   ' Make sure passed-in value is a date.  
   If Not IsDate(dteBirthdate) Then 
      dteBirthdate = Date 
   End If 
    
   ' Make sure birthdate is not in the future.  
   ' If it is, use today's date. 
   If dteBirthdate > Date Then 
      dteBirthdate = Date 
   End If 
    
   ' Calculate the difference in years between today and birthdate.  
   lngAge = DateDiff("yyyy", dteBirthdate, Date) 
   ' If birthdate has not occurred this year, subtract 1 from age.  
   If DateSerial(Year(Date), Month(dteBirthdate), Day(dteBirthdate)) > Date Then 
      lngAge = lngAge - 1 
   End If 
   CalcAge = lngAge 
End Function