"Θα έχω γράψει δέκα βιβλία μέχρι το καλοκαίρι."
Translation:I will have written ten books by the summer.
"Until" shows duration not time. So we can say: "I'll wait here until 4 o'clock." But "Dinner will be ready "by" 4 o'clock."
Jaye, an answer in another sentence " will you have talked until then" is incorrect which may lead people astray.
It's not incorrect but really, seriously ambiguous. Without context, it could have either "until" or "by". "Until" indicating the the 'duration' while "by" meaning "will you have made your statement before that time". Sorry, very clumsy interpretation. We have corrected it giving "Will you have talked by then? as the preferred sentence " but left the "until" just in case someone remembers it and gets confused. They'll be informed that by is the preferred word. Thanks a lot.
Until, indeed does show duration and refers "up to" the specific point in time, in this case summer ( Needless to say I used until!)
Exactly in the sentence here, we are looking for an action that will have been completed by a certain time in the future in which case "until" would not be suitable.