Maybe this then?

DAY(DATE(YEAR(GOMONTH(tdate,1)),MONTH(GOMONTH(tDate,1)),1)-1)

Alan

>No, it does not work either.
>Try tdate={^2000-05-31} for instance.
>
>>Good call Yuri,
>>
>>But this will work:
>>

>>day(gomonth(tDate-DAY(tdate),1))
>>

>>
>>Glenn
>>
>>>Glenn,
>>>
>>>It will not work. For instance, try tdate={^2003-01-31}
>>>
>>>>You can try:
>>>>

>>>>Function DaysInMonth
>>>>lpar tDate
>>>>return day(gomonth(tDate,1)-day(tDate))
>>>>

>>>>
>>>>Glenn
>>>>>Is there a function available to calulate the # of days in a given month from a date() function?
>>>>>
>>>>>Jeff