How long is sunscreen good for, if it has been two years past the expiry date?

Sunscreen. As an absolute efficacy endpoint, it is probably not good one year after it expires. Practically speaking though, and because it is so cheap and effective when used properly in the prevention of skin cancer, buy a new one to start the season. By the way, I just saw a report that 5+ blistering sunburns IN YOUR LIFETIME, increases skin cancer risks. So, lather up with lotion!!!
Throw it out. You should buy a new bottle! Expiration dates are there for a reason. You should discard sunscreens one month after expiration. .