An expiration date system contains a time release mechanism for marking a predetermined interval of time in the range from six months to one year. The mechanism contains a vessel, in which there are brought together in any order a) water, b) a neutralizer, c) a source of oxygen, and d) a hydroquinone compound, such that the pH of the contents of the vessel is greater than 7.0 and the interval being marked begins when the last of items a), b), c) and d) is brought into the presence of the other items and the interval is a function of the pH and of the temperature.