adding th,nd or st to a date

Wednesday 02 April 2008 12:39:03 pm

Hi,
I have the following:

{$this_object.data_map.date.content.timestamp|datetime(custom,"%l %j,")}

Is there a way I can ensure that the date has "th", "nd" or "st" is appended to the data on display?

I cannot see a way to do it on the docs....granted I skimmed over the them!

;-)

Thanks

Tony