If you refer to Telerik Reporting Graph item, by default the axis will use CategoryScale where labels are recognized as strings. To change the formatting in thic case you can work with the CategoryGroups - grouping - Label and place a proper expression formatting the labels.
Other approach is to switch to DateTime scale and use the axis LabelFormat - How to: Change the Axis Scale
Data point labels have their own DataPointLabel settings
, which will be applied on individual points in the Graph.
I hope the information is helpful.
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