You can try using DateSerial() function.
DateSerial returns a Date value for the specified year, month and day. It also handles relative Date expressions.
A Date value.
DateSerial returns a Date value for the specified year, month and day. It also handles relative Date expressions.
DateSerial (2000, 6, 15)
DateSerial (2004, 1 - 7, 15)
DateSerial (2008, 1, 166)
Check the below code as it finds the first day of next month and then you can go back one day back to get last date of month.
DateSerial ( year({table.date}, month({table.date}) + 1, 1 - 1 ; )
You can refer this link to know more about this function −