I am assuming if you are reading this article you have hit the frustrating wall of your custom date refiner showing the graph and slider incorrectly. The refiner looks correct until you actually use the refiner and realize that range is numeric instead of last year, six months, etc!
Well if you are looking for a fix you are in the right spot friend. The refiner is not working correctly due to your managed property name! Believe it or not the managed property name will impact the date slider refiner.
For this example I have created a new managed property of date type called date_Published which has an associated crawled property and all of the correct settings. When I modify my refinement panel and add date_Published as a refiner using the slider with bar graph, it looks correct but the values are all numeric integers!
After a great deal of sleuthing I realized that if you append on two numbers to the end of your managed property between 0 – 9 the property will render correctly, aka managed_PropName[0-9][0-9]. When I updated my managed property to the name date_Published85 the refiner rendered correctly!
Hope This Helps!