Refrigerated Milk

Hello! I was wondering if anyone knew how long breastmilk is good for once taken from the refrigerator if you don’t warm it? I expressed milk yesterday and kept it in the fridge overnight. Today we are going out and I’m going to express fresh milk for that. But I’m wondering for the future if I want to put it in a bottle and take it with me without warming it, how long will it last? I don’t have a cooler yet, so My question is referring to a cold bottle put in my diaper bag. Thank you!