The Maximum and Minimum values of RadSlider are of type double. Therefore, if MinValue and MaxValue are of type DateTime, you will need to use a converter to pass a valid double value when binding.
The way RadSlider works is that the data context of each tick is the value at the corresponding position. Therefore, if you want to convert the double value to a DateTime and show it in the TextBox, you will have to use another converter. I have attached a sample project demonstrating this functionality. Currently, when using a Converter in the TickTemplate causes the RadSlider to not measure its ticks properly. This limitation will be fixed for our official release, which is scheduled for the mid of March. Have a look at it and let me know if you have additional questions or comments on the topic.
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