يا ترى الخطا فين:I will have finished this book until tomorrow.

[ابو بيشو]

اليك منى كل احترام وتقدير

I will have finished this book by tomorrow.
Until is used for an action or state continuing up to a certain time: 'The
shops are open until five thirty.' 'I'll wait here until you get back.'
By is used for an action which happens before or no later than a certain
time: 'I have to submit my dissertation by the end of next year.'