When buying your bread, look at the plastic tab, the color denotes when it was delivered to the store.
Just spread out a single layer evenly on a plate and microwave for 5-20 seconds. Start out at 5 seconds and increase in 5 second intervals until you get to know how strong your microwave is. Let it cool down and it will be as fresh and crunchy as new! Super easy solution to not wasting food!