(Leftover from ticket #11092 which moved the unit display names data into a new "unit" tree for ICU 54.)
We keep having users who need a small subset of ICU. In particular, we have users who only need very basic services like some Unicode properties, and list and number formatting, plural & gender.
However, our core locale data is fairly large. We have split the data files into multiple trees before, and I would like us to do more of that now. Splitting by functionality is easily handled via dependency rules in product builds. (As opposed to splitting by language, or filtering subsets of same-type data.)
I propose that we move the date/time formatting data (the "calendar", "durationUnits" and "fields" top-level items) into a separate "date" tree.