JDE Excel Date Conversion
Julain to Gregorian Date
=DATE(YEAR("01/01/"&TEXT(1900+INT(A1/1000),0)),MONTH("01/01/"&TEXT(1900+INT(A1/1000),0)),DAY("01/01/"&TEXT(1900+INT(A1/1000),0)))+MOD(A1,1000)-1
Gregorian to Julian
=(YEAR(A1)-2000+100)*1000+A1-DATE(YEAR(A1),"01","01")+1
