Like a fine wine, freshness is not always superior to age and the hard-boiled egg is another example of this. The fresher the egg is that you have purchased to hard-boil, the more difficult it is likely going to be to remove the peel. The older the egg, the easier. 

The Anatomy of an Egg

Understanding the anatomy of an egg can help you to understand why an older egg peels more easily than a fresher does.  An egg consists of a shell, inner and outer membranes, air cell, albumen, chalazae, vitelline membrane, and a yolk.  The air cell is located between the inner and outer membranes at the wider end of the egg and is a result of the cooling process that occurs within the egg after it is laid. 

Air Cells Grow with Age

As the egg ages this air cell grows larger.  The air cell accounts for the cause of an older egg floating while a younger egg does not.  It also accounts for the depression that frequently occurs at the larger end of an egg after it is hard-boiled, the shell collapsing into the air cell.

Hard-boiled Eggs are better with Age

Oddly, when it comes to hard-boiling eggs, freshness is not preferable.  Ultimately, the larger the air space between the hard outer shell and the inner membrane the easier the egg is going to be to peel. Purchasing eggs a week to ten days prior to use should do the trick and result in an egg that is easy to peel as well as safe to eat.

Tip: If you are unsure of the age of the egg, you can try the water float test.  The more buoyant an egg in water, the older the egg.  If your egg has a foul odor after cooking do not ingest it.

Tip: Some experts suggest that you poke a pinhole in the bottom of the egg so that the air cell will release its air and when the white portion of the egg hits the boiling water it will seal the hole resulting in better shaped eggs with fewer cracks.