We need to set scaleType property of Axis as "datetime" to work with datetime axis. By default axis scale type is "numeric". Once you set the axisScale property as datetime, Axis will consider x values of all the data points as DateTime. x can be just timestamp in millisecond or javascript Date Object. Next you might want to change the datetime format displaced on Axis scale. You need to set valueFormat property in Axis to format the date and time values at once.

A Chart with DateTime x-axis & numeric y-axis