On your marks. Get set. Go!
Some deals are not for OneDayOnly but, instead, run for limited amounts of time during the day.
A "Lunchtime Deal" is a single deal with limited stock that runs for 1 hour from 13:00 every day.
A "Dinner Deal" is a limited-time deal that runs for 1-2 hours on some evenings and can also have limited stock. These run on random days though, unlike the Lunchtime Deals (LTD).
Basically...fastest fingers first. Limited stock. Limited time.
Unfortunately, you are unable to add the above "speed sale" deals to an order you have already placed.