Date calculation functions

Description - Saw a Summit session about tracking progress to goal using cumulative functions (which I'd never used before honestly).  While doing it I realized Adobe, for all it's functions, does not have date calculation functions.  So you could do, say a calculate of the different between today and Jan 1 and then be able to display how many days in the year have elapsed or calculate the % of year elapsed.  I've see some of this done using the rowcount function but then you need to have all your table rows displayed all the time, which is a pain.

Why is this feature important to you -  I'd like to really leverage goal progress more in dashboards and this would really help show where we are today vs where we should be.  I could calculate the YTD % of days and dynamically multiply it by my goal to easily displey where we should be TODAY vs where we actually are

How would you like the feature to work - In the calculated metric column, add a new function DateDiff that can caluclate the number between two days (fixed or dynamic)  This is already used in the rolling date ranges function for time segments.

Current Behaviour -  Only way to simulate this (I know of( is with lots of tables with rowcount functions but only works if all your metrics need the exact same number of rows.