How to get an array of the previous months/date from a given date/month?

How to get an array of the previous months/date from a given date/month?

I want to have a script that would also generate the last 23 months prior
to a certain/given date in this format: MMM YY
For example,
The given date is 2013-09-15 (YYYY-MM-DD) or Sep 13 (MMM YY)
The script will then get the last 23 months prior to the end date. It
should output/list months starting from Oct 11 up to Sep 13.
Thank you so much.