This is a "discuss" topic for revision of the "LDML-spec"
The two part AM/PM day division is not universal and some cultures require
greater grandularity in day divisions to properly represent a time. The
requester has not made a comprehensive investigation of the issue but is aware
of at least 4 nations (having 10s of languages) where the requirement occurs. It
is likely the norm in communities of the developing world where clocks and
watches are luxury items and people rely on solar observations to discern time,
or where the division names from this practice have survived into the present
The following extension to LDML would be minimally sufficient to represent the
division names and periods:
The <dayDivision> tags would be interpretted to indicate that the enclosed name
should be displayed on and after the indicated "start" time.
An example, while the <am> and <pm> remain convenient short hand for
representing day divisions for the bulk of the world's cultures, the proposed
structure remains compatible: