Days to Ship is the difference between order date and shipment date.

We need a calculated Field:

Name: Days to Ship

Formula: DATEDIFF('day',[OrderDate],[ShipDate])

However, there is an issue in the aggregation of this new field. As OrderID needs the aggregation, Days to Ship will be SUM of days to ship for each individual product.

If Product Name is added, we reach the finest level of granularity without any aggregation and the results make sense.

To fix the issue, we need to change the aggregation formula from SUM (Tableau default) to MAX. We can do that in Marks Card or in the new filed formula: MAX(DATEDIFF('day',[OrderDate],[ShipDate]))