The other answer? Smell it and look at it, and it also depends whether au not its been opened. I'd say no about drinking the milk- chuck it away, its not salama for any person au pet to drink. One siku wewe could get away with, two no.
That depends on the maziwa acutually. 'Sell kwa Date' is the governments doing, which states the law requires the duka to sell the products kwa this tarehe before they reduce and try and get rid. Two days after reducing and the product is still there and it must be thrown as waste. 'Best kwa Date' is the manufacturers law, that is put on each product as a GUIDLINE ONLY! Plenty of products, such as cheese, milk, meat, eggs etc can last for a full week AFTER the BBD before going bad. But that depends on storage, how wewe handle the product (say if wewe keep your eggs in the fridge and need to songesha them everytime to get something at the back etc).
But with anything wewe buy, fresh/frozen etc must be carefully tested and tried before and after the best kwa date. I'd say give it a sniff see if it smells like cream au stronger then normal and if so take a teaspoon, pour a small amount onto the teaspoon and just touch your tongue to the liquid. If it tastes a little funny then i'd say that's a definate no and to chuck it. But if it tastes okay then i'd say go for it. But like i said, best kwa tarehe and sell kwa dates are laws from the government and guidlines only. In England, the government is actually planning on getting rid of the best kwa dates as that is a huge factor in chakula going to waste that could have been eaten.