In Cell Formats, versions 643c, 1.0.1, 1.0.3.1 and 1.1beta2 had "1999" ("YYYY") 
formatting for an option. We have added a "1" (week of the year) and removed 
"1999" (year).  In other words 1.1RC1 removed a commonly used date format and 
replaced it with a very infrequently used date format.  

I propose one of two (or both) solutions:
(1) that the "1999" be added back.  I know I can add the format to a 
spreadsheet, but it has to be done every time and needs to be standard.
(2) allow adding a custom format and have it saved as a permanent format by the 
user (when the user needs custom formats).  The user who uses a custom format 
for one spreadsheet likely wants it for more than one and shouldn't have to keep 
adding it, so "saving" it, "editing" it or "deleting" it should be options 
available to the user along with the present "for this spreadsheet only" current 
non-option.