Can any date function solve this problem?

[kwons9]

Is there anyway make this query shorter?
Vintage(Month of action) is always end date of the action month. I need to define this from Jan 2004 to the most current month.
Is there any fuction can do it automatically?

Many thanks,

/*=========Define Vintage==========*/
when EVNT_PROC_DT between '2005-05-01' and '2005-05-31' then cast('2005-05-31' as date)
when EVNT_PROC_DT between '2005-06-01' and '2005-06-30' then cast('2005-06-30' as date)
when EVNT_PROC_DT between '2005-07-01' and '2005-07-31' then cast('2005-07-31' as date)
when EVNT_PROC_DT between '2005-08-01' and '2005-08-31' then cast('2005-08-31' as date)
when EVNT_PROC_DT between '2005-09-01' and '2005-09-30' then cast('2005-09-30' as date)
when EVNT_PROC_DT between '2005-10-01' and '2005-10-31' then cast('2005-10-31' as date)
when EVNT_PROC_DT between '2005-11-01' and '2005-11-30' then cast('2005-11-30' as date)
else null end as vintage,

 

[al1024]

To get the date of last day of month, you can try this expression :
add_months(EVNT_PROC_DT + 1 - extract(day from EVNT_PROC_DT), 1) - 1