I searched the forum and didn't find this even though it was there, so I am just making a post with the instructions right here, hopefully it will be easier for others to find.
Info copied from this thread: https://www.mobileread.com/forums/sho...t=21988&page=2
Problem: your borrowed ebook won't open, you're getting a message "this book is not active yet
How to set the cybook internal clock so your books will open:
1) In a text editor, create a file with the current date and time in this format:
save the file, naming it rtc.dat
An example file is attached.
2) Plug your Cybook to your computer through USB and delete all time bomb ebooks from your library (files initially transferred from your public library).
3) Copy the "rtc.dat" file to the Cybook "/system" folder.
4) Unplug your Cybook.
5) When you are back on the "Library", switch off your Cybook.
6) Switch on your Cybook.
7) Plug the USB cable again and copy your public library titles to the Cybook (or to the SD card) "/eBooks" folder.
8) By the way, you can check that the "rtc.dat" was automatically deleted (i.e. taken into account) from the "/system" folder.
9) Unplug, when you are back on the "Library", you should be able to open the public library titles.
This should be a one time procedure to set your system date which will stay coherent thanks to the internal clock battery. (according to bookeen)
There is a wiki page listing some libraries where you can borrow ebooks; if you know of more libraries, you're welcome and encouraged to add your information to the wiki.