Counting days on a report [Closed]

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I need help with counting days if there is not an end date on the report.
Ex: Count the days from the admission date to the end of the month I am doing the report if there is no admit date. If there is an admit and discharge date would I just use the DAYS360 formula?
My work wants to know what amount of days a patient was at our hospital from admit date to discharge date but some patients haven't discharged yet so I would want to count the days from admit to the end of the month that I am doing the report.