How long has that burrito been sitting in your refrigerator? When did that milk expire? While some things are fairly obviously past their prime, there are others in your refrigerator that may deserve to be thrown out, so on November 15, celebrate National Clean Out Your Refrigerator Day.

While this is only one day a year, GQ Magazine recommends that you clean your refrigerator every three or four months. Condiments, opened containers and other items can sometimes escape notice and it is worthwhile to take three or four times a year to keep them from taking up space. This is a great day to start.

In some families, there are weekly leftovers nights, where dinner is made up of previous meals and then what’s left over is thrown away. It may be a family tradition for some people, but National Clean Out Your Refrigerator Day didn’t become national until 1999.

Why should you clean your refrigerator? Well, according to bustle.com and thespruce.com,  if you don’t clean your refrigerator or at least check if something needs to be thrown out, mold and mildew will start to grow in your refrigerator.

If you consume something that has gone bad, you may experience symptoms related to food poisoning, such as fever, chills, stomach cramps, diarrhea, nausea, and vomiting. These symptoms can last for several hours and maybe even several days. You shouldn’t necessarily rely on expiration dates to tell you whether or not something has gone bad. Did you know expiration dates are not required by any federal law, but in some states they only require it on meat or milk?

While we take refrigeration for granted, it is a practice that was invented by a Scottish scientist named William Cullen in the 1740s, but the first refrigerator wasn’t available until 1899. (History). Before that, nobody bothered to clean out a refrigerator, because they didn’t exist. Now that they do, make sure to keep it clean!