# Backcasting

This week, we will show how to make a backward forecast using only NumXL functions in Excel. We will also discuss the relationship between a regular time series model and an implied backward/reversed time series model.

Why do we care? Backward forecasting is a vital tool in time series analysis. For instance, we can apply it to fill-in missing values using both sides of the gap for imputation. In addition, backcasting allows the re-creation of historical events within a model, and thus, finding increasing applications in macroeconomic time series models.

For more details, see the following article: Time series backward forecasting