The term safety time is defined as the number of days (working days) that arrival is desired, in relation to when the requirement occurs or emerges. The safety time be used to compensate for uncertainties in consumption.
The safety stock indicates at which stock level that a requirement emerges, and the safety time indicated at which point in time (date) that you want the delivery to arrive. Safety time is therefore applied when you use order suggestions during requirement calculations. You can also use safety times for structure orders for manufacturing orders, in order to configure a finish time for underlying level manufactured parts.
If the system has been configured to show the period in the date format YYWW, the Order Window and other windows will be displayed in weeks. It would then be appropriate to enter the value in number of weeks x 5, since the working days unit is always entered.