What does “for a limited period of time” mean? For how long and when can I borrow books?

Books from the study room can be borrowed for the weekend only. You can borrow books on Friday after 12:00 a.m. and they must be returned until 12.00 a.m. the following Monday at the latest. During the holidays there is a different period of borrowing books. The date and time of possible lending and the necessity of returning books is announced on the message board in the study room and on the website of the Institute of Scientific Information at http://knihovna.lf2.cuni.cz/ in advance.

What does “for a limited period of time” mean? For how long and when can I borrow books?
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