A Colorado family was accidentally living like it was 1999 this week after they allegedly bought a box of cereal from Walmart, ate some of it, and then discovered the cereal had expired during the last season of Seinfeld.

According to The Denver Channel, Anthea and Josiah Carelse say they bought a box of Quaker 100% Natural Granola cereal from Walmart on Monday, March 5, 2018. They say they’d picked it up off the shelf at the store, so there was no reason to think anything about their purchase was amiss. After taking a few bites, however, Anthea Carelse says she thought something tasted off. Her husband ate a whole bowl, though he agreed the taste was “funny.” After checking the box, however, they say they were shocked to discover the box had a “best by” date of February 21, 1997. That means the box had just celebrated its 21st birthday when the Carelses bought it.

The UPC code of the out-of-date box matches the number on the Carelses’ Walmart receipt from this week.

The last time it was OK to eat the Carelses’ cereal, Hong Kong was still under British rule. Married… with Children and Seinfeld were still on the air, and South Park had just debuted.

Josiah Carelse says he’s feeling fine after eating the 21-year-old cereal, but he intends to take the box back to the store for a refund. For more breakfast nutrition, check out the healthiest and unhealthiest breakfast cereals.