Returns or sets the base unit for the specified category axis.xlDays - Days, xlMonths - Months, xlYears - Years.
Setting this property has no visible effect if the CategoryType property for the specified axis is set to xlCategoryScale. The set value is retained, however, and takes effect when the CategoryType property is set to xlTimeScale. You cannot set this property for a value axis.
ActiveChart.Axes(1).BaseUnit = xlDays