system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Difference in "Sell By," "Best by," and expiration dates?

How long does food usually last, and in what quality, up to these dates? I feel like they all mean something different if not similar, yet I only ever see one on something that I buy.
gpt
* A "Sell-By" date tells the store how long to display the product for sale. You should buy the product before the date expires. It is a stock control system for the stores. 
* A "Best By (or Before)" date is recommended for best flavor or quality. It is not a purchase or safety date. It is a guarantee for the consumer that if you use the food on or before the date listed, it should taste fresh. It is advisory only and says nothing about the safety (or lack thereof) of the food on or after a certain date. 
* A "Use By" date is generally a date at which food is no longer considered safe to eat. You might see something like "Keep refrigerated and use within 5 days of opening" on a carton of egg whites, for example. You should not get sick if you eat within 5 days - you may get sick after 5 days.