This is not really a question but more of a solution. I have been searching for a select statement for X day of previous month. There are many helpful solutions for first day and last day but I never found a solution for say the 20th day of the previous month. Sure I could just use DATEPART but I needed it in datetime format to insert in an SSRS report for a parameter default value. I wanted to share the solution I came up with and see if anyone has anything better.
In the following query I am selecting the first day of last month then adding 19 days so I can get the 20th day of the previous month.
Select DATEADD(day, 19,DATEADD(month, DATEDIFF(month, 0, GETDATE())-1, 0))