Specific date in Tender Validity Deadline (BT-98)

Several of our users would like to specify a specific date (instead of a duration) as the tender validity deadline (currently BT-98). Is there a reason why a time period must be specified here? If not, would it be conceivable to specify a duration or a specific date (perhaps in a new/own BT (similar to GR-Lot-PlannedDuration))?

Background: The awarding organisations like to set a validity deadline until the (fixed) start date. With the current solution, they therefore have to count/calculate the days in order to specify the desired binding period.