How to: Fill in months automatically.
Solution:
Select the first or the first few cells containing the starting months for the series. Drag the fill handle over the range to fill.
1) Select the first or the first few cells containing the starting months for the series.
NOTE: Selecting the first few cells allows Excel to determine the difference between two cells, if the difference is a value other than 1, and increment or decrement the series accordingly.
2) Drag the fill handle over the range to fill.
AutoFilling the range
NOTE: To fill the range in increasing order, drag down or to the right. To fill the range in decreasing order, drag up or to the left.