In Japan there are two types of dates commonly seen of food products: best before and expiration. Products often only have one of the two so it is best if you learn how to read the kanji for each type (賞味期限 = best before and 消費期限 = expiration).
When reading dates, also keep in mind that Japanese dates are typically written with the year first as Year.Month.Date. For example, February 27th 2021 would be written as: 2021.02.27 or 21.02.27.
Best before date
賞味期限 (しょうみきげん - shoumikigen)
賞味期限 is the “best before” date for a product. This means that a product will taste as intended by the manufacturer before this date. Shomikigen is used for products that don’t spoil easily and have long shelf lives such as dashi, snacks, and frozen food. For example, on a senbei (japanese rice cracker) you may see shoumikigen as an indication of when the product may start to lose its freshness. Keep in mind these dates tend to be quite conservative and don't necessarily mean the product will go bad on this date. You can think of this more as a "sell by" date.
消費期限 (しょうひきげん - shouhikigen)
消費期限 is the expiration date of a product and is used for fresh products that spoil easily. This includes items such as bentos, fresh meat, and some sweets. If you see a product that is heavily discounted, make sure to check the expiration date as it is often within a 48 hour period of when you are making your purchase.
Though this is a different system then the simple expiration dates that is used elsewhere, we hope this understanding helps you to further explore Japanese ingredients!
Learn how to read nutrition labels in Japan.