You can determine the date of manufacture by looking at the bottom dome of the can for a 5-digit number. The first two numbers indicate the year of manufacture, while the last three numbers indicate the day of the year. For instance, 21032 would mean the 32nd day of 2021, i.e. February 1, 2021. Formally, our fuel additives have a 2-year shelf life, but their practical shelf life is at least 5 years if sealed.