You may well ask why I want to know this, in view of our current weather, but here goes anyway:
A couple of years ago I bought a bottle of sunscreen - factor 30 - as I needed it in California. I haven't been anywhere similar since then, and I don't sunbathe; the bottle is still three-quarters full. I can't see a 'use-by' date on it; do you think it's still a) effective and b) safe?