default a date to last day of month in IDT

Hi guys

I need to convert some dates in a table to default to the end of month...

Here is what I want to do

Existing_Date                                                     Expected result

2015-04-01 00:00:00000                                    30/04/2015 12:00:00 AM

2017-01-01 00:00:0000                                      31/07/2017 12:00:00 AM

What function can I use to convert this to end of month dates?

cheers