If you need to calculate the current age of a participant after you collect the participant's birth date, you can use this following in an Equation Type question. The following example assumes the date type question has the code
DateofBirth:
{floor((time() - mktime(0,0,0,substr(DateofBirth,5,2),substr(DateofBirth,8,2),substr(DateofBirth,0,4)))/(365.25*24*60*60))}
