Bought a pack of uncooked chicken pieces and a rack of pork ribs from the supermarket on Sunday - use by dates of 29th & 30th. I opened the packets as i wanted to marinate the meat but am now wondering if the same use by dates apply as i have opened the packaging?

the answer is undoubtedly 'no'

there's usually something along the lines of 'once opened consume within 2 days' or similar..............

Thanks, that's what i thought but had thrown the packaging away! I know they have a 2 or 3 day rule on lunch type/processed meats, but wasn't sure on other cuts.

Put it to your nose.

Chicken you won't even have to do that if it is off.

I thought they put nitrogen into the packaging instead of normal air and so that changes the "use by" date once it's opened and the contents now in ordinary air.