The time::chrono submodule provides the basis for chronology in Hare, namely
[[timescale]]s (leap second handling), [[timezone]]s, and the [[moment]] type,
an abstracted date/time object for external modules to interface with.

For working with the ISO 8601 Gregorian calendar, see the [[datetime]] module.

Hare defines a chronology as a system used to name and order moments in time. In
practice, a chronology is the combination of a calendar (for handling days) and
a wall clock (for handling times throughout a day).

This module implements a small chronology of dates & times. A moment observes
certain chronological values according to its [[locality]]. The "observe"
functions [[date]], [[time]], and [[zone]] obtain these values.

Higher level modules like [[datetime]] expand upon this with more complex
chronological values (years, hours, etc.). The [[datetime::datetime]] type
embeds [[moment]], and other modules implementing other chronologies may
interoperate with their own extension types.

[[time::instant]]s can be [[convert]]ed via the [[timescale]] interface. The
[[tai]] timescale acts as the central intermediary timescale. Other timescales
are expected to be able to convert their instants to TAI and back.
