Hi,
to display a julian date you can use the J symbol in your display pattern:
date{YYJ} to display January the 3rd 2015 as 153 (3rd day in 2015)
or
date{YYJJJ} to display January the 3rd 2015 as 15003 (with leading zeros)
To reuse the formatted Date in a script use the formattedValue instead of the rawValue.