The following can be used in a Math column to obtain an Ordinal Date in the format YYYYDDD

Year(Date) * 1000
+ FLOOR(275 * MONTH(Date)  / 9)
- (FLOOR((MONTH(Date) + 9) / 12)
* (1 + FLOOR((YEAR(Date) - 4 * FLOOR(YEAR(Date) / 4) + 2) / 3)))
+ DAY(Date)
- 30