I make a shipment today and try to schedule a pickup. The shipment is dated today, but the cutcuff to schedule a pickup is midnight last night. I can't schedule the pickup today because it's past the cutoff, and I can't schedule a pickup for tomorrow because the shipment is dated today.
I should be able to schedule a pickup tomorrow for any pending shipment, even shipments that were dated earlier. This is also a problem if, say, your courier misses a scheduled pickup. In the current system it would never get picked up because you can't schedule a pickup for past shipments, only if the dates are exactly the same.