I just looked at the date code on my bottle last night. 16 118, or April 28th normally, April 27th this year because of Leap year! So my stuff is roughly a month old.

I don't think it matters much in my case and so far seems to be working just fine with my test numbers showing results. I need to find time to test the potency and see if its running true to 10%. Either way I doubt it would be significantly lower than 10%, or lower than the Great Value 8.25% Bleach I'd been buying for $2.94/gal which still leaves me in the good since it's only $2.50/gal.