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.