Previous Month from a Date Column in Query Editor

So I have to do this in Query Editor. I have a date column that has various dates like 2/1/16, 3/3/16, 4/2/16, etc.. I need to create a column with a date that is the last day of the previous month based on this date column. So the result from the previous dates would be 1/31/16, 2/29/16, 3/31/16, etc. 

Not very familiar with M Code so I'm unsure how to do this. I can't just subtract one day since the date column could be the second or third day or so into the next month.