I am trying to get an offset to the week number (custom date expression %U), as in I want to start the week number from a certain date. I wonder what this Off (up/down control box) do? It is located next to the Cent. box. in the number 8 group of controls called "Auto Date (8)".
http://postimg.org/image/sga9wlub9/
I have looked and searched the manual for the past 30 minutes to no avail. Please add this information to the Custom Date Formats help page.