It seems JDEdwards dates are stored NUMERIC(6, 0) in this format 107299, where 107 is the number of years after 1900, and 299 is the 299th day of the year.
So how to convert JDEdwards to DATETIME?
DECLARE @jde NUMERIC(6, 0)
SET @jde = 107299
SELECT @jde,
DATEADD(DAY, @jde % 1000, DATEADD(YEAR, @jde / 1000, -1))
And how to go from DATETIME to JDEdwards?
DECLARE @Date DATETIME
SET @Date = '20041117'
SELECT @Date,
1000 * DATEDIFF(YEAR, 0, @Date) + DATEPART(DAYOFYEAR, @Date)