For generating a range of Excel dates a month apart you can use this formula: =DATE(2012, MONTH,28) where MONTH is a positive integer. Specifying a month value greater than 12 correctly adjusts the year.
Example
=DATE(2012,14,28) returns 2013-02-28
Here’s a dirty little hack for generating a vertical list of dates exactly a month apart — it uses the current row to increment the month value:
=DATE(2012,CELL(“row”, A1),28)