I was installing the training kit listed at following URL for a client.
I try to activate the feature in created training site when I got above error message. The site was configured to run under English (Australia) in the site regional settings.
To fix above problem you need to change the site regional settings for English (United State).
The feature can be only activated on the training site if the site regional setting is set to English (Unites sate). This is documented in the installation guide with more details.