Rolling Age based on Datediff - Need a Solution

[stevie_westside]

Hi All, I just can't figure this out... working on this problem for days and I have no solution.  Looking to the pros...

I have 148,876 shipment dates

I have a simple date table starting 01/01/2018 to present day.

I need a few things:

1.  On any given date (from the date table), how many of the 148K shipment dates were 0-6 months old, 6-12, 12-18, and 18-24.

2.  On any given date (from the date table), what was the average age of the 148K shipments?

3.  Now I need the same as 1 & 2, but it needs to be aggregated into weeks, not days.  For example, 01/01/2018 is a Monday, 01/08/2018 is a Sunday.  For this week specifically (and every week thereafter):

  - how many of the 148K shipment dates were 0-6 months old, 6-12, 12-18, and 18-24.

  - what was the average age of the 148K shipments?

Ideas?  My brain melted a few days ago, I'm in need of assistance.