Though Foursquare is often used to find out which locations are most frequented by the people you know, a new website inversely uses it to determine when places are visited the least. When Should I Visit? uses data gathered from Foursquare to find the least busy times to visit the museums, galleries and theaters of London. It also displays the quietest days along with a graph to judge the relative popularity of different days.  Creator Dan Williams explains:

The data used to calculate when museums are quiet is gathered from foursquare. Foursquare is designed to show popular trending places or where your friends are. I instead used it for antisocial purposes.

The advantage of using foursquare is that it is not tied to the institutions listed. New places can be added and removed, even non-cultural organisations. However foursquare users represent only a certain demographic of attendees. This may be considered a feature if you wish to avoid foursquare users. I hope to get hold of admissions data from some of the museums listed to verify how accurate When Should I Visit? is.

When Should I Visit