How to: Format Axis Labels as Dates or Currencies
When you show properly formatted DateTime values on an axis, a chart will automatically display these values as days. To specify a date/time interval for the x-axis, such as an interval of months or an interval of hours, you must format the axis labels and set the type of axis interval to a valid date or time interval.
In order to format time intervals correctly, the values displayed on the x-axis must evaluate to a System.DateTime data type. If your field has a data type of System.String, the chart will not calculate intervals as dates or times. For more information, see Preparing Data for Display in a Chart Data Region.
When a numeric value is added to the y-axis, by default, the chart does not format the number before displaying it. If your numeric field is a sales figure, consider formatting the numbers as currencies to increase the readability of the chart.
To format x-axis labels as monthly intervals
- Right-click the x-axis of the chart, and select Axis Properties. 
- In the CategoryAxis Properties dialog box, select Label Format. 
- From the Category list, select Date. From the Type list, select a date format to apply to the x-axis labels. 
- Select Axis Options. 
- In Interval, type 1. In Interval type property, select Months. - Note - If you do not specify an interval type, the chart will calculate intervals in terms of days. 
- Click OK. 
To format y-axis labels using a currency format
- Right-click the y-axis of the chart, and select Axis Properties. 
- In the Value Axis Properties dialog box, select Label Format. 
- From the Category list, select Currency. From the Type list, select a currency format to apply to the y-axis labels. 
- Click OK.