Convert Julian date to standard date.

I am querying a ctree database, from ms access that has dates and times stored in the Julian date format. I would like to locate a function to convert the date to the format MM/DD/YYYY. E.g 2454398 is 10/24/2007 and 4417338 is 12:16 pm. None of the formula’s I have seen so far work with this date and time format.