How long can you leave milk out before it spoils?

It'll be OK. It depends on the surrounding temperature, but if it wasn't too hot you'll be OK. But you do need to run down to the store and get yourself a new quart. It will spoil faster, now that it's been out and about for a bit.

It really matters what the temperature is when it is removed from refrigeration. An hour is normally ok, especially since it tasted fine to you. Don't drink anything that appears curdled, or has a strong odor. Don't ever leave dairy items, including mayonnaise, in direct sunlight, without ice for very long. People forget that at the beach and picnics, for instance. More illness from that than almost all other dairy items combined.

It may remain in room temperature (25c) for up to 4 hours, however, you should always store it in the refrigerator or freezer as soon as you can. You can store breast milk in the fridge for up to 5 days in the summer time and about a week in winter. Note that breast milk must be in the back of the refrigerator where it is cooler than the front. In the freezer, it can remain for 3-4 months. When you defrost it, use it in the following 24 fours and do it in a bowl of hot water (60c top) or under streaming hot water, but never in the microwave or you will ruin everything good about it.

depends on the room temperature .. but keeping it out for more than 2 hours is risky

only ,1 hour?..its ok,no problem