Your eggs can sit on the grocery store shelf for up to 45 days before they are pulled. They are still good, but they must be sold within 45 days of when they are washed and packaged.
Personally, I've kept store bought eggs in my fridge for months and months and months and never had a problem. But if you're wondering if your eggs are still good, there's a very simple test that will tell you: put the egg in a bowl of water.
The floating egg needs to find its way to the compost pile. The eggs resting on the bottom are still good and should be enjoyed with a big helping of bacon. But buy eggs from your local farmer, not the grocery store. They're better for you and taste better too!