Return the creation time of the specified LogRecord as formatted text.
This method should be called from format() by a formatter which
wants to make use of a formatted time. This method can be overridden
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, 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.
3.3: Previously, the default 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 have a format placeholder for milliseconds, the millisecond value is appended using another format string, '%s,%03d' — and both of these format strings have been hardcoded into this method. With the change, these strings are defined as class-level attributes which can be overridden at the instance level when desired. The names of the attributes are default_time_format (for the strptime format string) and default_msec_format (for appending the millisecond value).