I'm reeling with shock that anyone can buy a pint of milk and it lasts long enough to go off!
I buy a six pint of semi and four pints each of whole and skimmed milk twice a week. The children and one of my lodgers have whole milk, husband and I drink skimmed and the other people in the house and most visitors have semi. I always keep a six pack of UHT milk in too because there are times when I'm running low on milk and it's my standby and it's also brilliant for making yoghurt.
Anyway I digress, here's what t'internet has to say about it:
Few people drink full-cream milk these days – they prefer the lower fat options of skimmed or semi-skimmed milk. Interestingly, these spoil quicker than whole milk because there are extra stages in the manufacturing process where the fat is taken out, and in the case of semi-skimmed, some put back again, before the product is packaged. This provides more opportunities for microbial contamination.