The universe is about 14 billion years old, so a million years is one fourteen-thousandth of the age of the universe. Now, an actual eyeblink takes about 300 m

The universe is about 14 billion years old, so a million years is one fourteen-thousandth of the age of the universe. Now, an actual eyeblink takes about 300 milliseconds, so a million years is to the age of the universe as the blink of an eye is to 70 minutes. So the metaphor seems reasonable to me.