Age at Risk (AaR) is a time-based risk measure designed to measure longevity risk in actuarial models. AaR represents certain quantile for a given probability distribution, so is similar to Value at Risk (VaR).But, AaR measures risk amount as time(time until an adverse event) rather than value(loss amount). Age at Risk is a special case of Time at Risk (TaR). When TaR is applied to a household's financial planning rather than corporate finance,TaR in this case is referred to as AaR.