Age from Date of Birth using JQuery

You might find the open source Datejs library to be helpful. Specifically the the addYears function.

var dob = Date.parse($(this).text());
if (dob.addYears(18) < Date.today())
{
    $(this).text("Under 18");
}
else
{
    $(this).text(" Over 18");
}

In a more terse fashion:

$(this).text(
    Date.parse($(this).text()).addYears(18) < Date.today() ?
    "Under 18" :
    " Over 18"
)

Date.prototype.age=function(at){
    var value = new Date(this.getTime());
    var age = at.getFullYear() - value.getFullYear();
    value = value.setFullYear(at.getFullYear());
    if (at < value) --age;
    return age;
};

var dob = new Date(Date.parse($(this).text()));

if(dob.age(new Date()) < 18)
{
    $(this).text("Under 18");
}
else
{
    $(this).text(" Over 18");
}