Calculating age in years from DOB

IF(

  MONTH(TODAY())>MONTH(DOB__c),

    YEAR(TODAY())-YEAR(DOB__c),

    IF(AND(MONTH(TODAY()) = MONTH(DOB__c), DAY(TODAY()) >= DAY(DOB__c)),

      YEAR(TODAY())-YEAR(DOB__c),

      (YEAR(TODAY())-YEAR(DOB__c))-1)

)




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