on my last business trip to London, I looked at all of the sunscreens at Boots, Superdrugs, etc... they all had "markings" that told how long they were good after opening ( as an example "good for 12 months after opening" ), but none had an expiration date (as in the US) stating that it should not be used after a certain date (whether opened or not). There have been several times in the US that I have not bought sunscreens because they expired in a few months ...How do you know if the sunscreen has expired even if it has not been opened? None of the sales people could help me.... thanks...