Is a reference any good if it's a few months old?

Got a reference from my current employer 2 months ago when I was applying for a course. It's a very positive one. In all honesty, my workplace is a cesspool of, at best, incompetence, at worst, outright hostility and abuse. Could write a list of illegal practices. I handed in my notice 5 days ago, I've 9 days left.

I almost hit breaking point of walking out mid shift when my boss screamed at me, in front of customers. She had decided that morning that customers couldn't dine outside anymore. 3 couples in their 70s couldn't understand why they suddenly couldn't eat outside when they did yesterday. In all honesty one or 2 of them probably had dementia or something and they were all shakey and staggering, the poor wee things. I must've said it 4 times and was crazy busy, I didnt have time to argue with some elderly guests who were 100% in the right and couldn't seem to follow a basic conversation. When their food came out, the most sturdy of them took a tray and carried it out himself. I admired it. They had already paid me, why the f shouldn't they enjoy their criminally overpriced food outside? She said I needed to make them come inside pronto and it was a good 100 feet from the bar, that's so unfair on them. If I do leave the next time she pulls nonsense like this, can I still use my old reference? I'm bracing for the worst case scenario.