formatting and manipulation. For related

functionality, see also the :mod:`time` and :mod:`calendar` modules.

There are two kinds of date and time objects: "naive" and "aware". This

distinction refers to whether the object has any notion of time zone, daylight

saving time, or other kind of algorithmic or political time adjustment. Whether

a naive :class:`.datetime` object represents Coordinated Universal Time (UTC),

local time, or time in some other timezone is purely up to the program, just

like it's up to the program whether a particular number represents metres,

miles, or mass. Naive :class:`.datetime` objects are easy to understand and to

work with, at the cost of ignoring some aspects of reality.

For applications requiring more, :class:`.datetime` and :class:`.time` objects

have an optional time zone information attribute, :attr:`tzinfo`, that can be

set to an instance of a subclass of the abstract :class:`tzinfo` class. These

:class:`tzinfo` objects capture information about the offset from UTC time, the

time zone name, and whether Daylight Saving Time is in effect. Note that only

one concrete :class:`tzinfo` class, the :class:`timezone` class, is supplied by the

:mod:`datetime` module. The :class:`timezone` class can represent simple

timezones with fixed offset from UTC such as UTC itself or North American EST and

EDT timezones. Supporting timezones at whatever level of detail is

required is up to the application. The rules for time adjustment across the

An object *d* of type :class:`.time` or :class:`.datetime` may be naive or aware.

*d* is aware if ``d.tzinfo`` is not ``None`` and ``d.tzinfo.utcoffset(d)`` does

not return ``None``. If ``d.tzinfo`` is ``None``, or if ``d.tzinfo`` is not

``None`` but ``d.tzinfo.utcoffset(d)`` returns ``None``, *d* is naive.