1. X axis displays values beginning from 0 in DateTime
I was not able to reproduce this. I created a simple project and it plots the dates correctly. I have attached the project to this post (also included a snapshot of the output, look for attachment XAxisSampleDateTime1), so that you can test it and see if you get the same results. If you get correct results with the sample project I have provided and errenous results with your project I suggest that you compare the code to find the differences and hopefully discover what causes the incorrect labels' text.
When data is sampled a few data items are clustered (summarized) into a single data point. This is the reason the DataItem of the data point is null, which results in invalid tooltips. I can suggest that you use the Custom Sampling Functions
to be able to show proper information in the tool tips. I have also attached a project that demonstrates this(attachment CustomSamplingFunctionsAndToolTips) to get you started.
I hope the above is of help.
the Telerik team
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