bpo-33400: Clarified documentation to indicate no strict adherence to ISO 8601. (GH-6703)

(cherry picked from commit c4994dc0)
Co-authored-by: Vinay Sajip <vinay_sajip@yahoo.co.uk>

Doc/howto/logging.rst

@@ -296,9 +296,9 @@ which should print something like this:
 
    2010-12-12 11:41:42,612 is when this event was logged.
 
-The default format for date/time display (shown above) is ISO8601. If you need
-more control over the formatting of the date/time, provide a *datefmt*
-argument to ``basicConfig``, as in this example::
+The default format for date/time display (shown above) is like ISO8601 or
+RFC 3339. If you need more control over the formatting of the date/time, provide
+a *datefmt* argument to ``basicConfig``, as in this example::
 
    import logging
    logging.basicConfig(format='%(asctime)s %(message)s', datefmt='%m/%d/%Y %I:%M:%S %p')

Doc/library/logging.config.rst

@@ -783,10 +783,10 @@ Sections which specify formatter configuration are typified by the following.
 
 The ``format`` entry is the overall format string, and the ``datefmt`` entry is
 the :func:`strftime`\ -compatible date/time format string.  If empty, the
-package substitutes ISO8601 format date/times, which is almost equivalent to
-specifying the date format string ``'%Y-%m-%d %H:%M:%S'``.  The ISO8601 format
-also specifies milliseconds, which are appended to the result of using the above
-format string, with a comma separator.  An example time in ISO8601 format is
+package substitutes ISO8601-style format date/times, which is almost equivalent to
+specifying the date format string ``'%Y-%m-%d %H:%M:%S'``.  This format also
+specifies milliseconds, which are appended to the result of using the above
+format string, with a comma separator.  An example time in this format is
 ``2003-01-23 00:29:50,411``.
 
 The ``class`` entry is optional.  It indicates the name of the formatter's class

Doc/library/logging.rst

@@ -515,8 +515,9 @@ The useful mapping keys in a :class:`LogRecord` are given in the section on
    Returns a new instance of the :class:`Formatter` class.  The instance is
    initialized with a format string for the message as a whole, as well as a
    format string for the date/time portion of a message.  If no *fmt* is
-   specified, ``'%(message)s'`` is used.  If no *datefmt* is specified, the
-   ISO8601 date format is used.
+   specified, ``'%(message)s'`` is used.  If no *datefmt* is specified, an
+   ISO8601-like (or RFC3339-like) date format is used. See the
+   :meth:`formatTime` documentation for more details.
 
    The *style* parameter can be one of '%', '{' or '$' and determines how
    the format string will be merged with its data: using one of %-formatting,
@@ -556,8 +557,8 @@ The useful mapping keys in a :class:`LogRecord` are given in the section on
       formatters to provide for any specific requirement, but the basic behavior
       is as follows: if *datefmt* (a string) is specified, it is used with
       :func:`time.strftime` to format the creation time of the
-      record. Otherwise, the ISO8601 format is used.  The resulting string is
-      returned.
+      record. Otherwise, an ISO8601-like (or RDC 3339-like) format is used.  The
+      resulting string is returned.
 
       This function uses a user-configurable function to convert the creation
       time to a tuple. By default, :func:`time.localtime` is used; to change
@@ -568,7 +569,7 @@ The useful mapping keys in a :class:`LogRecord` are given in the section on
       attribute in the ``Formatter`` class.
 
       .. versionchanged:: 3.3
-         Previously, the default ISO 8601 format was hard-coded as in this
+         Previously, the default ISO8601-like format was hard-coded as in this
          example: ``2010-09-06 22:38:15,292`` where the part before the comma is
          handled by a strptime format string (``'%Y-%m-%d %H:%M:%S'``), and the
          part after the comma is a millisecond value. Because strptime does not

Lib/logging/__init__.py

@@ -473,7 +473,8 @@ class Formatter(object):
 
         Initialize the formatter either with the specified format string, or a
         default as described above. Allow for specialized date formatting with
-        the optional datefmt argument (if omitted, you get the ISO8601 format).
+        the optional datefmt argument. If datefmt is omitted, you get an
+        ISO8601-like (or RFC 3339-like) format.
 
         Use a style parameter of '%', '{' or '$' to specify that you want to
         use one of %-formatting, :meth:`str.format` (``{}``) formatting or
@@ -501,13 +502,13 @@ class Formatter(object):
         in formatters to provide for any specific requirement, but the
         basic behaviour is as follows: if datefmt (a string) is specified,
         it is used with time.strftime() to format the creation time of the
-        record. Otherwise, the ISO8601 format is used. The resulting
-        string is returned. This function uses a user-configurable function
-        to convert the creation time to a tuple. By default, time.localtime()
-        is used; to change this for a particular formatter instance, set the
-        'converter' attribute to a function with the same signature as
-        time.localtime() or time.gmtime(). To change it for all formatters,
-        for example if you want all logging times to be shown in GMT,
+        record. Otherwise, an ISO8601-like (or RFC 3339-like) format is used.
+        The resulting string is returned. This function uses a user-configurable
+        function to convert the creation time to a tuple. By default,
+        time.localtime() is used; to change this for a particular formatter
+        instance, set the 'converter' attribute to a function with the same
+        signature as time.localtime() or time.gmtime(). To change it for all
+        formatters, for example if you want all logging times to be shown in GMT,
         set the 'converter' attribute in the Formatter class.
         """
         ct = self.converter(record.created)