Yogurt keeps for a very long time....just keeps getting more tangy.

Ditto. Milk doesn't “expire”. The date is the money back guarantee for freshness. All of it, commercial milk, is far from the cow. As long as it isn't ultrapasteurized or irradiated, i.e. dead, you should be able to make yoghurt. The whole point of yoghurt was originally preservation. If you store it air tight and vary cold, and you have't gotten any mold spores in it, it should last well.

My neighbour works in a shelter and she's always bringing home cartons of milk that are near or on the expiry date. She's been giving some to me lately, and I've never had them sour, even days afterwards.

Last week she gave me 2x2-litre cartons of homo (which I never buy) so I made rice pudding and scalloped potatoes. She gave me a carton of 2% this week, expired on the 1st, and I just finished it, no problem with it souring.

Homo and 2% are just too rich, I like 1% so I just add some water to it.

Lucky you, Jasdip, for being the recipient, but the only reasons I can think of for the shelter not using the up the milk is either that they have more coming in a contract milk order and the one or two cartons aren't enough for them to make enough of a dish for everybody, or that if the date is the problem, it's a CYA thing, if people in Canada file as many ridiculous lawsuits as they do here. It's far more important to smell and taste the milk, to make sure it's good, even though the expiration date isn't for a couple of weeks! The date isn't a guarantee. Besides whether the store will back it up if it's sour before, it helps you keep track of which is the older carton, to use first.

Ok I made yogurt last night. I will check it out later today. Five pint jars fit into my instant pot. I usually just make it in the pot itself but I recently ordered a couple of different cultures from Positively Probiotic. Last night I made yogurt from some Cabot I had on hand and made a second batch of Dahi from PP. Their cultures require several steps to activate. I am not sure if it is worth it unless I particularly love one. They have a daunting list of cultures.

Plllog because it's a shelter, I believe it's a health rule. They're certainly being over-stringent. The staff throws it all out, it's only recently that my neighbour started bringing it home. and thankfully I'm a lucky recipient.

FWIW, I understand in some places, milk can have a extra short 'use by' date...

https://99percentinvisible.org/episode/best-enjoyed-by/

"...In 1977, the New York State Consumer Protection Board published a booklet called Blind Dates: How to Break the Codes on the Foods You Buy. The booklet told consumers how to decipher the encrypted date codes on their favorite products. The board distributed more than 10,000 copies and posted the booklet in supermarkets.Image courtesy of Mark Turnauckas

Eventually, consumers started to demand that these dates be put clearly on packaging, and retailers and grocery stores responded. A few states began to regulate these date labels, but there was no federal-level regulation, even though there were a number of attempts. Still, consumers wanted freshness dates, so all kinds of different ones popped up (“use-by”, “sell-by”, “best-by”, “best if used by,” “expires on”). Some dates were stamped right on the product, some printed on the label. There was no consistency in how this information was displayed or the language that was used.

Some companies even tried to use “freshness dating” to sell their products, like in this Pepsi commercial:

Some date labels were meant for consumers, while others were just meant for retailers. And as is still true now, There were no clear definitions for any of the phrases and no consistency even within the same brand or product. Dates could differ from state-to-state, manufacturer-to-manufacturer, or store-to-store.This product is best if used by July, 1716. Image courtesy of Lynn Friedman

Over the years we’ve lost track of what these labels meant in the first place. We’ve come to associate the dates with safety, when in fact, they’ve always been about freshness. As much as we might want them to, the dates on our food are not going to tell us if we’ll get salmonella or e-coli.

Most date labels are arrived at by conducting taste tests. Does a product still taste good on day 4? Day 5?

And yet today, according to a report that Emily Broad-Leib co-authored, a majority of consumers believe that eating food past it’s sell-by or use-by date is a risk to their health. And as many as 90% of Americans throw out food based on date labels at least occasionally...."

You can freeze milk.