To use the Forecasting System, your data set must be dated: the data set must contain a time ID variable that gives the date of each observation. The time ID variable must represent the observation dates with SAS date values or with SAS datetime values (for hourly data or other frequencies less than a day), or you can use a simple time index.

When SAS date values are used, the ID variable contains dates within the time periods corresponding to the observations. For example, for monthly data, the values for the time ID variable can be the date of the first day of the month corresponding to each observation, or the time ID variable can contain the date of the last day in the month. (Any date within the period serves as the time ID for the observation.)

If your data set already contains a valid time ID variable with SAS date or datetime values, the next step is to specify this time ID variable in the Time ID field. If the time ID variable is named DATE, the system fills in the Time ID field automatically.

If your data set does not contain a time ID, you must add a valid time ID variable before beginning the forecasting process. The Forecasting System provides features that make this easy to do. See Chapter 40, Creating Time ID Variables, for details.