Find the Latest Date in a Series

I have an app in which we create invoices, each with various service line items that were performed on various dates.  Our payer requires that the payment "request date" be one day after the last service line item date.  We want Knack to calculate this automatically. Now Knack has functions that can look at related tables and calculate various things such as the Max, Min, Avg, or Count.  Although it does not have a function that looks at dates.  So, to do this follow these instructions: 1) Convert Date to a Number in the Connected Object (uses Unix Time based on January 1, 1970). 2) In the Invoice Object, Apply the Max Function to the Date “Number”. 3) This will result in the highest number.

4) Convert that number back to a Date.