You need to tell us more - a lot more. What reader? What files? What computer? Full text of the error message? And there's a whole forum for ADEPT.....
Moving this discussion to the Adobe Digital Editions forum.
The original message was:
"Trying to download ebooks to Adobe Digital Editions but got the message:
What should I do so that I can download again.
Also, why can I not download these files to my e-reader?
The error message means that the time, timezone on or date is not set correctly on your computer.