How to know the date of photo/video taken after downloaded from icloud website?
Problem #1: You'll probably need to download iCloud. Apps are almost always more fully featured than websites, because of their capability to access your hardware, and their lack of web security limitations.

Problem #2: You may not be able to fix this. If you can't find the date anywhere on iCloud.com, or through the iCloud app, it may be data that doesn't exist.

Tips: Try using Chrome instead of Firefox. If you are on a Mac, use Safari.

Tips for getting iCloud app to work: Restart your computer. Turn off Windows Security Center and your firewall (temporarily). Don't forget to turn those back on when you have successfully installed and run iCloud.