This document discusses different methods for measuring forecast accuracy. It covers quantity accuracy, time accuracy, and a combined measure of total forecast accuracy. For quantity accuracy, common metrics include mean error, mean square error, mean absolute deviation, and mean absolute percentage error. Time accuracy considers how accurate the forecast is in predicting the actual time period and accounts for forecasts that are preponed or postponed. The document proposes formulas for calculating overall quantity accuracy and time accuracy and combining them into a single total forecast accuracy measure.