Currently the system entities for date and time make a guess to fill in portions of the date and time that are not mentioned by the user.
"Monday" could be in the future or in the past.
"4/5" could be this year, last year or next year.
"five o'clock" could be AM or PM.
"September" could be in the past or in the future.
The person writing the dialog tree knows whether they would expect a date in the past or in the future, but currently there's no way to hint that to the system entity.
This idea is for the sys-date entity to have an attribute or method that allows for getting the date within the bounds expected. For example sys-date.future() or sys-date.past() or sys-date.within(start, end). These functions could return null if the date cannot be interpreted to fall within the specified bounds.