Do Sheet Masks Expire?

We know how it feels to receive a 'been waiting' product only to peek at the worrying number on the back of the package. Then we quickly think in our head "Why does it say 2017? It's already 2018... Has this expired? Should I sue the company?"
So we are here to tell you more about the 'numbers' on the back of the package.
You might be looking at a manufacturing date instead of an expiration date. Unsurprisingly, K-beauty products have decided to print all these confusing numbers in Korean. If you want to make sure the product you are using isn't expired, get a closer look at this!
제조 -> Manufacturing Date
까지 -> Expiration Date
사용기한 -> Use By
Korean companies tend to print manufacturing dates to inform customers that they are getting fresh products. Having a separate manufacturing date and an expiration date is really for the benefits of the consumers. For an example, an expiration date is the last day the product can be distributed. Rarely anyone would like to buy a product that is so close to the expiration date because that means you'll have less time to use it. On the other hand, if you buy a product from a fresh batch, you will have more time to use the product. However, this is referring to its shelf life before opening. Once you open a product, it will oxidize/ be exposed to bacteria. So don't open the product thinking you have the date until the expiration date to use them.
Typically, Asian countries have a different order for their dates. The dates you're looking at might look like this: 20180730, these numbers are written in the following format: YYYY/MM/DD.
Sheet masks' shelf life before opening is about 1-3 years. Some sheet masks do indicate the expiration date, but some have a manufacturing date on them. If your product is missing an expiration date, an unopened mask can usually have a shelf life of 24-36 months.
Not to mention, sheet masks don't have a shelf life after opening, meaning you have to use them immediately!