Flickr api : photos.getCounts

I’m trying to use the flickr api method photos.getCounts … its supposed to return me a count of how many photos exist in a date range.

this is the method :
http://www.flickr.com/services/api/explore/?method=flickr.photos.getCounts

and i’m testing it out with their api explorer
http://www.flickr.com/services/api/explore/?method=flickr.photos.getCounts

So i put in two timestamps for a range, separated with a comma like they said

but it returns nothing?