Glossary

Horology

The study of and measurement of time. (definition)

Unit

A unit of time. Normally, a typed quantity.

Part

A measure of a particular unit in a Time instance. Often with regards to a whole.

Whole

The unit that a selected part should be aligned to. Often, the of keyword parameter refers to a whole. In comments, it can be referred to as of-whole.

Point

A point in time, however, it is a misleading designation as Points in Time are always vectors. Essentially, they can be treated as Points or as Vectors. It is a scalar quantity relative to a datum and with a magnitude of no less than one unit of the scalar quantity.

PiT

Shorthand for: Point in Time.

Subsecond

Often, a reference to the precision of representation type.

Representation Type

An actual Python class representing a [unit] Type defined in a Time Context.

Time Context

An instance of core.Context managing the set of defined unit Types and any corresponding Representation Types.

Canonical Position

A PiT that is in the understood time zone that does not vary. Usually referring to UTC.

Localization

Referring to the process of localizing a timestamp to a particular time zone. Given a UTC timestamp, a localized version of the timestamp would be the timestamp adjusted by the offset identified by the specified zone.Zone. zone.Zone.localize.

Normalization

Referring the process of normalizing a localized timestamp to a particular time zone. Given a localized timestamp, a normalized version of the timestamp would be the timestamp adjusted to UTC and then localized. Normalization should be used when representing timestamps whose localized version has been manipulated. zone.Zone.normalize.

Term

Internal use only; a core unit. Units are associated as "like" terms by libunit.Context instances. In the default context, there are only two terms: days and months.

Bridge

Internal use only; a set of mappings that allow "unlike" terms to be converted. This is the infrastructure that provides a means to register the conversion methods for converting days to months and months to days.

Type

A particular unit of time in a Time Context. second, day, month are all types.

References

The functionality and API choices of a number of datetime implementations were analyzed during the development of chronometry:

• Chronus-ST (http://chronos-st.org/)

• SQL/Postgres' DATE, TIME, and TIMESTAMP types.

• Python datetime

• dateutils

• mxDateTime

• Datetime packages from java and ruby.

Wikipedia was, naturally, heavily referenced during the development of Chronometry.

• http://en.wikipedia.org/wiki/Second

• http://en.wikipedia.org/wiki/Julian_year_(astronomy)