Best if Used By... date?

My mom went food shopping about a week ago. She saw some cereal she wanted to try and bought it. Today (one week later) I thought about trying it. Out of curiosity I looked at the recommended date to eat it by and it said "April 1, 2015". I was like " What? Is this some April Fool's joke?". From my experience when buying cereal the date it's recommended to be eaten is usually about 6 months after I buy it. How long after the recommended eat or use by date can a food product be on the store shelf for?
This is just weird.
Best if Used By... date?
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