The Nova Project.

[Jonathan Meer]

When you click on a champion's name on the Guide page, you may get a list of guides, as they tend to have more than one guide for a champion. On that page, the time since the last update is indicated. Guides with a lower number for this value are more likely to be up-to-date than guides with a higher number for this value.

EDIT: I've taken the liberty of marking this number in red.

[spoiler][/spoiler]