I was being facetious (one of only two words in the English language to contain all five vowels in the correct order, by the way. Not a lot of people know that).
Where I live delivery slots from the big supermarkets were unavailable from March to July. They were briefly available during the summer but then became scarce towards the end of September before drying up completely again. It doesn't matter what time of day or night you search for one, which of the suppliers you choose or what day it is. There are simply none available. The same goes for "click & collect" slots.
That's why I chuckle when I read of people talking of their "regular weekly delivery from Tesco" and so on.