Every civilization now accumulates culture on a global level in addition to local city culture. Whenever it passes certain thresholds a Golden Age begins.
To install you only need to unpack the .zip in your Beyond the Sword\Mods folder.
Credit goes to Maniac who developed this mechanic for his excellent Planetfall mod, I merely cut it out so that it might find some use in other mods too or even be used as a standalone.
Cultural Golden Age 1.0
Civ wide culture is accumulated to trigger Golden Ages