As long as the yogurt doesn't smell or taste bad or the yogurt doesn't have any mold in it then yes it's safe to eat expired yogurt.
I've eaten yogurt that has expired as long as it's remained refrigerated and it didn't smell bad or taste bad.
Just because it's the yogurt has expired doesn't mean that the expired yogurt is bad but it just means that the yogurt has lost it's freshness.
It's best to eat the yogurt before it's expiration date for the best and freshest taste.
But usually if the yogurt has just expired for maybe a week or so the yogurt is usually still very good to eat but if the yogurt is a month or more expired then the yogurt might not be any good.
Just smell the yogurt and look for any mold and if it's moldy or smells bad then throw it out but if not it's still safe to eat.