content: """
  Matplotlib provides sophisticated date plotting capabilities, standing on the
  shoulders of python :mod:`datetime`, the add-on modules :mod:`pytz` and
  :mod:`dateutil`.  :class:`datetime` objects are converted to floating point
  numbers which represent time in days since 0001-01-01 UTC, plus 1.  For
  example, 0001-01-01, 06:00 is 1.25, not 0.25.  The helper functions
  :func:`date2num`, :func:`num2date` and :func:`drange` are used to facilitate
  easy conversion to and from :mod:`datetime` and numeric ranges.
  
  .. note::
  
     Like Python's datetime, mpl uses the Gregorian calendar for all
     conversions between dates and floating point numbers. This practice
     is not universal, and calendar differences can cause confusing
     differences between what Python and mpl give as the number of days
     since 0001-01-01 and what other software and databases yield.  For
     example, the US Naval Observatory uses a calendar that switches
     from Julian to Gregorian in October, 1582.  Hence, using their
     calculator, the number of days between 0001-01-01 and 2006-04-01 is
     732403, whereas using the Gregorian calendar via the datetime
     module we find::
  
       In [31]:date(2006,4,1).toordinal() - date(1,1,1).toordinal()
       Out[31]:732401
  
  
  A wide range of specific and general purpose date tick locators and
  formatters are provided in this module.  See
  :mod:`matplotlib.ticker` for general information on tick locators
  and formatters.  These are described below.
  
  All the matplotlib date converters, tickers and formatters are
  timezone aware, and the default timezone is given by the timezone
  parameter in your :file:`matplotlibrc` file.  If you leave out a
  :class:`tz` timezone instance, the default from your rc file will be
  assumed.  If you want to use a custom time zone, pass a
  :class:`pytz.timezone` instance with the tz keyword argument to
  :func:`num2date`, :func:`plot_date`, and any custom date tickers or
  locators you create.  See `pytz <http://pythonhosted.org/pytz/>`_ for
  information on :mod:`pytz` and timezone handling.
  
  The `dateutil module <https://dateutil.readthedocs.io/en/stable/>`_ provides
  additional code to handle date ticking, making it easy to place ticks
  on any kinds of dates.  See examples below.
  
  Date tickers
  ------------
  
  Most of the date tickers can locate single or multiple values.  For
  example::
  
      # import constants for the days of the week
      from matplotlib.dates import MO, TU, WE, TH, FR, SA, SU
  
      # tick on mondays every week
      loc = WeekdayLocator(byweekday=MO, tz=tz)
  
      # tick on mondays and saturdays
      loc = WeekdayLocator(byweekday=(MO, SA))
  
  In addition, most of the constructors take an interval argument::
  
      # tick on mondays every second week
      loc = WeekdayLocator(byweekday=MO, interval=2)
  
  The rrule locator allows completely general date ticking::
  
      # tick every 5th easter
      rule = rrulewrapper(YEARLY, byeaster=1, interval=5)
      loc = RRuleLocator(rule)
  
  Here are all the date tickers:
  
      * :class:`MinuteLocator`: locate minutes
  
      * :class:`HourLocator`: locate hours
  
      * :class:`DayLocator`: locate specifed days of the month
  
      * :class:`WeekdayLocator`: Locate days of the week, e.g., MO, TU
  
      * :class:`MonthLocator`: locate months, e.g., 7 for july
  
      * :class:`YearLocator`: locate years that are multiples of base
  
      * :class:`RRuleLocator`: locate using a
        :class:`matplotlib.dates.rrulewrapper`.  The
        :class:`rrulewrapper` is a simple wrapper around a
        :class:`dateutil.rrule` (`dateutil
        <https://dateutil.readthedocs.io/en/stable/>`_) which allow almost
        arbitrary date tick specifications.  See `rrule example
        <../examples/pylab_examples/date_demo_rrule.html>`_.
  
      * :class:`AutoDateLocator`: On autoscale, this class picks the best
        :class:`MultipleDateLocator` to set the view limits and the tick
        locations.
  
  Date formatters
  ---------------
  
  Here all all the date formatters:
  
      * :class:`AutoDateFormatter`: attempts to figure out the best format
        to use.  This is most useful when used with the :class:`AutoDateLocator`.
  
      * :class:`DateFormatter`: use :func:`strftime` format strings
  
      * :class:`IndexDateFormatter`: date plots with implicit *x*
        indexing.
  """
  from __future__ import (absolute_import, division, print_function,
                          unicode_literals)
  
  import six
  from six.moves import zip
  from matplotlib import rcParams
  import re
  import time
  import math
  import datetime
  
  import warnings
  
  
  from dateutil.rrule import (rrule, MO, TU, WE, TH, FR, SA, SU, YEARLY,
                              MONTHLY, WEEKLY, DAILY, HOURLY, MINUTELY,
                              SECONDLY)
  from dateutil.relativedelta import relativedelta
  import dateutil.parser
  import numpy as np
  
  
  import matplotlib
  import matplotlib.units as units
  import matplotlib.cbook as cbook
  import matplotlib.ticker as ticker
  
  
  __all__ = ('date2num', 'num2date', 'drange', 'epoch2num',
             'num2epoch', 'mx2num', 'DateFormatter',
             'IndexDateFormatter', 'AutoDateFormatter', 'DateLocator',
             'RRuleLocator', 'AutoDateLocator', 'YearLocator',
             'MonthLocator', 'WeekdayLocator',
             'DayLocator', 'HourLocator', 'MinuteLocator',
             'SecondLocator', 'MicrosecondLocator',
             'rrule', 'MO', 'TU', 'WE', 'TH', 'FR', 'SA', 'SU',
             'YEARLY', 'MONTHLY', 'WEEKLY', 'DAILY',
             'HOURLY', 'MINUTELY', 'SECONDLY', 'MICROSECONDLY', 'relativedelta',
             'seconds', 'minutes', 'hours', 'weeks')
  
  
  # Make a simple UTC instance so we don't always have to import
  # pytz.  From the python datetime library docs:
  
  class _UTC(datetime.tzinfo):
      """UTC"""
  
      def utcoffset(self, dt):
          return datetime.timedelta(0)
  
      def tzname(self, dt):
          return str("UTC")
  
      def dst(self, dt):
          return datetime.timedelta(0)
  
  UTC = _UTC()
  
  
  def _get_rc_timezone():
      """
      Retrieve the preferred timeszone from the rcParams dictionary.
      """
      s = matplotlib.rcParams['timezone']
      if s == 'UTC':
          return UTC
      import pytz
      return pytz.timezone(s)
  
  """
  Time-related constants.
  """
  EPOCH_OFFSET = float(datetime.datetime(1970, 1, 1).toordinal())
  JULIAN_OFFSET = 1721424.5                         # Julian date at 0001-01-01
  MICROSECONDLY = SECONDLY + 1
  HOURS_PER_DAY = 24.
  MIN_PER_HOUR = 60.
  SEC_PER_MIN = 60.
  MONTHS_PER_YEAR = 12.
  
  DAYS_PER_WEEK = 7.
  DAYS_PER_MONTH = 30.
  DAYS_PER_YEAR = 365.0
  
  MINUTES_PER_DAY = MIN_PER_HOUR * HOURS_PER_DAY
  
  SEC_PER_HOUR = SEC_PER_MIN * MIN_PER_HOUR
  SEC_PER_DAY = SEC_PER_HOUR * HOURS_PER_DAY
  SEC_PER_WEEK = SEC_PER_DAY * DAYS_PER_WEEK
  
  MUSECONDS_PER_DAY = 1e6 * SEC_PER_DAY
  
  MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY = (
      MO, TU, WE, TH, FR, SA, SU)
  WEEKDAYS = (MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY)
  
  
  def _to_ordinalf(dt):
      """
      Convert :mod:`datetime` or :mod:`date` to the Gregorian date as UTC float
      days, preserving hours, minutes, seconds and microseconds.  Return value
      is a :func:`float`.
      """
      # Convert to UTC
      tzi = getattr(dt, 'tzinfo', None)
      if tzi is not None:
          dt = dt.astimezone(UTC)
          tzi = UTC
  
      base = float(dt.toordinal())
  
      # If it's sufficiently datetime-like, it will have a `date()` method
      cdate = getattr(dt, 'date', lambda: None)()
      if cdate is not None:
          # Get a datetime object at midnight UTC
          midnight_time = datetime.time(0, tzinfo=tzi)
  
          rdt = datetime.datetime.combine(cdate, midnight_time)
  
          # Append the seconds as a fraction of a day
          base += (dt - rdt).total_seconds() / SEC_PER_DAY
  
      return base
  
  
  # a version of _to_ordinalf that can operate on numpy arrays
  _to_ordinalf_np_vectorized = np.vectorize(_to_ordinalf)
  
  
  def _from_ordinalf(x, tz=None):
      """
      Convert Gregorian float of the date, preserving hours, minutes,
      seconds and microseconds.  Return value is a :class:`datetime`.
  
      The input date `x` is a float in ordinal days at UTC, and the output will
      be the specified :class:`datetime` object corresponding to that time in
      timezone `tz`, or if `tz` is `None`, in the timezone specified in
      `rcParams['timezone']`.
      """
      if tz is None:
          tz = _get_rc_timezone()
  
      ix = int(x)
      dt = datetime.datetime.fromordinal(ix).replace(tzinfo=UTC)
  
      remainder = float(x) - ix
  
      # Round down to the nearest microsecond.
      dt += datetime.timedelta(microseconds=int(remainder * MUSECONDS_PER_DAY))
  
      # Compensate for rounding errors
      if dt.microsecond < 10:
          dt = dt.replace(microsecond=0)
      elif dt.microsecond > 999990:
          dt += datetime.timedelta(microseconds=1e6 - dt.microsecond)
  
      return dt.astimezone(tz)
  
  
  # a version of _from_ordinalf that can operate on numpy arrays
  _from_ordinalf_np_vectorized = np.vectorize(_from_ordinalf)
  
  
  class strpdate2num(object):
      """
      Use this class to parse date strings to matplotlib datenums when
      you know the date format string of the date you are parsing.
      """
      def __init__(self, fmt):
          """ fmt: any valid strptime format is supported """
          self.fmt = fmt
  
      def __call__(self, s):
          """s : string to be converted
             return value: a date2num float
          """
          return date2num(datetime.datetime(*time.strptime(s, self.fmt)[:6]))
  
  
  class bytespdate2num(strpdate2num):
      """
      Use this class to parse date strings to matplotlib datenums when
      you know the date format string of the date you are parsing.  See
      :file:`examples/pylab_examples/load_converter.py`.
      """
      def __init__(self, fmt, encoding='utf-8'):
          """
          Args:
              fmt: any valid strptime format is supported
              encoding: encoding to use on byte input (default: 'utf-8')
          """
          super(bytespdate2num, self).__init__(fmt)
          self.encoding = encoding
  
      def __call__(self, b):
          """
          Args:
              b: byte input to be converted
          Returns:
              A date2num float
          """
          s = b.decode(self.encoding)
          return super(bytespdate2num, self).__call__(s)
  
  
  # a version of dateutil.parser.parse that can operate on nump0y arrays
  _dateutil_parser_parse_np_vectorized = np.vectorize(dateutil.parser.parse)
  
  
  def datestr2num(d, default=None):
      """
      Convert a date string to a datenum using
      :func:`dateutil.parser.parse`.
  
      Parameters
      ----------
      d : string or sequence of strings
          The dates to convert.
  
      default : datetime instance
          The default date to use when fields are missing in `d`.
      """
      if cbook.is_string_like(d):
          dt = dateutil.parser.parse(d, default=default)
          return date2num(dt)
      else:
          if default is not None:
              d = [dateutil.parser.parse(s, default=default) for s in d]
          d = np.asarray(d)
          if not d.size:
              return d
          return date2num(_dateutil_parser_parse_np_vectorized(d))
  
  
  def date2num(d):
      """
      *d* is either a :class:`datetime` instance or a sequence of datetimes.
  
      Return value is a floating point number (or sequence of floats)
      which gives the number of days (fraction part represents hours,
      minutes, seconds) since 0001-01-01 00:00:00 UTC, *plus* *one*.
      The addition of one here is a historical artifact.  Also, note
      that the Gregorian calendar is assumed; this is not universal
      practice.  For details, see the module docstring.
      """
      if not cbook.iterable(d):
          return _to_ordinalf(d)
      else:
          d = np.asarray(d)
          if not d.size:
              return d
          return _to_ordinalf_np_vectorized(d)
  
  
  def julian2num(j):
      """
      Convert a Julian date (or sequence) to a matplotlib date (or sequence).
      """
      if cbook.iterable(j):
          j = np.asarray(j)
      return j - JULIAN_OFFSET
  
  
  def num2julian(n):
      """
      Convert a matplotlib date (or sequence) to a Julian date (or sequence).
      """
      if cbook.iterable(n):
          n = np.asarray(n)
      return n + JULIAN_OFFSET
  
  
  def num2date(x, tz=None):
      """
      *x* is a float value which gives the number of days
      (fraction part represents hours, minutes, seconds) since
      0001-01-01 00:00:00 UTC *plus* *one*.
      The addition of one here is a historical artifact.  Also, note
      that the Gregorian calendar is assumed; this is not universal
      practice.  For details, see the module docstring.
  
      Return value is a :class:`datetime` instance in timezone *tz* (default to
      rcparams TZ value).
  
      If *x* is a sequence, a sequence of :class:`datetime` objects will
      be returned.
      """
      if tz is None:
          tz = _get_rc_timezone()
      if not cbook.iterable(x):
          return _from_ordinalf(x, tz)
      else:
          x = np.asarray(x)
          if not x.size:
              return x
          return _from_ordinalf_np_vectorized(x, tz).tolist()
  
  
  def drange(dstart, dend, delta):
      """
      Return a date range as float Gregorian ordinals.  *dstart* and
      *dend* are :class:`datetime` instances.  *delta* is a
      :class:`datetime.timedelta` instance.
      """
      f1 = _to_ordinalf(dstart)
      f2 = _to_ordinalf(dend)
      step = delta.total_seconds() / SEC_PER_DAY
  
      # calculate the difference between dend and dstart in times of delta
      num = int(np.ceil((f2 - f1) / step))
  
      # calculate end of the interval which will be generated
      dinterval_end = dstart + num * delta
  
      # ensure, that an half open interval will be generated [dstart, dend)
      if dinterval_end >= dend:
          # if the endpoint is greated than dend, just subtract one delta
          dinterval_end -= delta
          num -= 1
  
      f2 = _to_ordinalf(dinterval_end)  # new float-endpoint
      return np.linspace(f1, f2, num + 1)
  
  ### date tickers and formatters ###
  
  
  class DateFormatter(ticker.Formatter):
      """
      Tick location is seconds since the epoch.  Use a :func:`strftime`
      format string.
  
      Python only supports :mod:`datetime` :func:`strftime` formatting
      for years greater than 1900.  Thanks to Andrew Dalke, Dalke
      Scientific Software who contributed the :func:`strftime` code
      below to include dates earlier than this year.
      """
  
      illegal_s = re.compile(r"((^|[^%])(%%)*%s)")
  
      def __init__(self, fmt, tz=None):
          """
          *fmt* is a :func:`strftime` format string; *tz* is the
           :class:`tzinfo` instance.
          """
          if tz is None:
              tz = _get_rc_timezone()
          self.fmt = fmt
          self.tz = tz
  
      def __call__(self, x, pos=0):
          if x == 0:
              raise ValueError('DateFormatter found a value of x=0, which is '
                               'an illegal date.  This usually occurs because '
                               'you have not informed the axis that it is '
                               'plotting dates, e.g., with ax.xaxis_date()')
          dt = num2date(x, self.tz)
          return self.strftime(dt, self.fmt)
  
      def set_tzinfo(self, tz):
          self.tz = tz
  
      def _replace_common_substr(self, s1, s2, sub1, sub2, replacement):
          """Helper function for replacing substrings sub1 and sub2
          located at the same indexes in strings s1 and s2 respectively,
          with the string replacement.  It is expected that sub1 and sub2
          have the same length.  Returns the pair s1, s2 after the
          substitutions.
          """
          # Find common indexes of substrings sub1 in s1 and sub2 in s2
          # and make substitutions inplace. Because this is inplace,
          # it is okay if len(replacement) != len(sub1), len(sub2).
          i = 0
          while True:
              j = s1.find(sub1, i)
              if j == -1:
                  break
  
              i = j + 1
              if s2[j:j + len(sub2)] != sub2:
                  continue
  
              s1 = s1[:j] + replacement + s1[j + len(sub1):]
              s2 = s2[:j] + replacement + s2[j + len(sub2):]
  
          return s1, s2
  
      def strftime_pre_1900(self, dt, fmt=None):
          """Call time.strftime for years before 1900 by rolling
          forward a multiple of 28 years.
  
          *fmt* is a :func:`strftime` format string.
  
          Dalke: I hope I did this math right.  Every 28 years the
          calendar repeats, except through century leap years excepting
          the 400 year leap years.  But only if you're using the Gregorian
          calendar.
          """
          if fmt is None:
              fmt = self.fmt
  
          # Since python's time module's strftime implementation does not
          # support %f microsecond (but the datetime module does), use a
          # regular expression substitution to replace instances of %f.
          # Note that this can be useful since python's floating-point
          # precision representation for datetime causes precision to be
          # more accurate closer to year 0 (around the year 2000, precision
          # can be at 10s of microseconds).
          fmt = re.sub(r'((^|[^%])(%%)*)%f',
                       r'\g<1>{0:06d}'.format(dt.microsecond), fmt)
  
          year = dt.year
          # For every non-leap year century, advance by
          # 6 years to get into the 28-year repeat cycle
          delta = 2000 - year
          off = 6 * (delta // 100 + delta // 400)
          year = year + off
  
          # Move to between the years 1973 and 2000
          year1 = year + ((2000 - year) // 28) * 28
          year2 = year1 + 28
          timetuple = dt.timetuple()
          # Generate timestamp string for year and year+28
          s1 = time.strftime(fmt, (year1,) + timetuple[1:])
          s2 = time.strftime(fmt, (year2,) + timetuple[1:])
  
          # Replace instances of respective years (both 2-digit and 4-digit)
          # that are located at the same indexes of s1, s2 with dt's year.
          # Note that C++'s strftime implementation does not use padded
          # zeros or padded whitespace for %y or %Y for years before 100, but
          # uses padded zeros for %x. (For example, try the runnable examples
          # with .tm_year in the interval [-1900, -1800] on
          # http://en.cppreference.com/w/c/chrono/strftime.) For ease of
          # implementation, we always use padded zeros for %y, %Y, and %x.
          s1, s2 = self._replace_common_substr(s1, s2,
                                               "{0:04d}".format(year1),
                                               "{0:04d}".format(year2),
                                               "{0:04d}".format(dt.year))
          s1, s2 = self._replace_common_substr(s1, s2,
                                               "{0:02d}".format(year1 % 100),
                                               "{0:02d}".format(year2 % 100),
                                               "{0:02d}".format(dt.year % 100))
          return cbook.unicode_safe(s1)
  
      def strftime(self, dt, fmt=None):
          """Refer to documentation for datetime.strftime.
  
          *fmt* is a :func:`strftime` format string.
  
          Warning: For years before 1900, depending upon the current
          locale it is possible that the year displayed with %x might
          be incorrect. For years before 100, %y and %Y will yield
          zero-padded strings.
          """
          if fmt is None:
              fmt = self.fmt
          fmt = self.illegal_s.sub(r"\1", fmt)
          fmt = fmt.replace("%s", "s")
          if dt.year >= 1900:
              # Note: in python 3.3 this is okay for years >= 1000,
              # refer to http://bugs.python.org/issue177742
              return cbook.unicode_safe(dt.strftime(fmt))
  
          return self.strftime_pre_1900(dt, fmt)
  
  
  class IndexDateFormatter(ticker.Formatter):
      """
      Use with :class:`~matplotlib.ticker.IndexLocator` to cycle format
      strings by index.
      """
      def __init__(self, t, fmt, tz=None):
          """
          *t* is a sequence of dates (floating point days).  *fmt* is a
          :func:`strftime` format string.
          """
          if tz is None:
              tz = _get_rc_timezone()
          self.t = t
          self.fmt = fmt
          self.tz = tz
  
      def __call__(self, x, pos=0):
          'Return the label for time *x* at position *pos*'
          ind = int(np.round(x))
          if ind >= len(self.t) or ind <= 0:
              return ''
  
          dt = num2date(self.t[ind], self.tz)
  
          return cbook.unicode_safe(dt.strftime(self.fmt))
  
  
  class AutoDateFormatter(ticker.Formatter):
      """
      This class attempts to figure out the best format to use.  This is
      most useful when used with the :class:`AutoDateLocator`.
  
  
      The AutoDateFormatter has a scale dictionary that maps the scale
      of the tick (the distance in days between one major tick) and a
      format string.  The default looks like this::
  
          self.scaled = {
              DAYS_PER_YEAR: rcParams['date.autoformat.year'],
              DAYS_PER_MONTH: rcParams['date.autoformat.month'],
              1.0: rcParams['date.autoformat.day'],
              1. / HOURS_PER_DAY: rcParams['date.autoformat.hour'],
              1. / (MINUTES_PER_DAY): rcParams['date.autoformat.minute'],
              1. / (SEC_PER_DAY): rcParams['date.autoformat.second'],
              1. / (MUSECONDS_PER_DAY): rcParams['date.autoformat.microsecond'],
              }
  
  
      The algorithm picks the key in the dictionary that is >= the
      current scale and uses that format string.  You can customize this
      dictionary by doing::
  
  
      >>> locator = AutoDateLocator()
      >>> formatter = AutoDateFormatter(locator)
      >>> formatter.scaled[1/(24.*60.)] = '%M:%S' # only show min and sec
  
      A custom :class:`~matplotlib.ticker.FuncFormatter` can also be used.
      The following example shows how to use a custom format function to strip
      trailing zeros from decimal seconds and adds the date to the first
      ticklabel::
  
          >>> def my_format_function(x, pos=None):
          ...     x = matplotlib.dates.num2date(x)
          ...     if pos == 0:
          ...         fmt = '%D %H:%M:%S.%f'
          ...     else:
          ...         fmt = '%H:%M:%S.%f'
          ...     label = x.strftime(fmt)
          ...     label = label.rstrip("0")
          ...     label = label.rstrip(".")
          ...     return label
          >>> from matplotlib.ticker import FuncFormatter
          >>> formatter.scaled[1/(24.*60.)] = FuncFormatter(my_format_function)
      """
  
      # This can be improved by providing some user-level direction on
      # how to choose the best format (precedence, etc...)
  
      # Perhaps a 'struct' that has a field for each time-type where a
      # zero would indicate "don't show" and a number would indicate
      # "show" with some sort of priority.  Same priorities could mean
      # show all with the same priority.
  
      # Or more simply, perhaps just a format string for each
      # possibility...
  
      def __init__(self, locator, tz=None, defaultfmt='%Y-%m-%d'):
          """
          Autoformat the date labels.  The default format is the one to use
          if none of the values in ``self.scaled`` are greater than the unit
          returned by ``locator._get_unit()``.
          """
          self._locator = locator
          self._tz = tz
          self.defaultfmt = defaultfmt
          self._formatter = DateFormatter(self.defaultfmt, tz)
          self.scaled = {DAYS_PER_YEAR: rcParams['date.autoformatter.year'],
                         DAYS_PER_MONTH: rcParams['date.autoformatter.month'],
                         1.0: rcParams['date.autoformatter.day'],
                         1. / HOURS_PER_DAY: rcParams['date.autoformatter.hour'],
                         1. / (MINUTES_PER_DAY):
                             rcParams['date.autoformatter.minute'],
                         1. / (SEC_PER_DAY):
                             rcParams['date.autoformatter.second'],
                         1. / (MUSECONDS_PER_DAY):
                             rcParams['date.autoformatter.microsecond']}
  
      def __call__(self, x, pos=None):
          locator_unit_scale = float(self._locator._get_unit())
          fmt = self.defaultfmt
  
          # Pick the first scale which is greater than the locator unit.
          for possible_scale in sorted(self.scaled):
              if possible_scale >= locator_unit_scale:
                  fmt = self.scaled[possible_scale]
                  break
  
          if isinstance(fmt, six.string_types):
              self._formatter = DateFormatter(fmt, self._tz)
              result = self._formatter(x, pos)
          elif six.callable(fmt):
              result = fmt(x, pos)
          else:
              raise TypeError('Unexpected type passed to {0!r}.'.format(self))
  
          return result
  
  
  class rrulewrapper(object):
  
      def __init__(self, freq, **kwargs):
          self._construct = kwargs.copy()
          self._construct["freq"] = freq
          self._rrule = rrule(**self._construct)
  
      def set(self, **kwargs):
          self._construct.update(kwargs)
          self._rrule = rrule(**self._construct)
  
      def __getattr__(self, name):
          if name in self.__dict__:
              return self.__dict__[name]
          return getattr(self._rrule, name)
  
  
  class DateLocator(ticker.Locator):
      """
      Determines the tick locations when plotting dates.
      """
      hms0d = {'byhour': 0, 'byminute': 0, 'bysecond': 0}
  
      def __init__(self, tz=None):
          """
          *tz* is a :class:`tzinfo` instance.
          """
          if tz is None:
              tz = _get_rc_timezone()
          self.tz = tz
  
      def set_tzinfo(self, tz):
          """
          Set time zone info.
          """
          self.tz = tz
  
      def datalim_to_dt(self):
          """
          Convert axis data interval to datetime objects.
          """
          dmin, dmax = self.axis.get_data_interval()
          if dmin > dmax:
              dmin, dmax = dmax, dmin
  
          return num2date(dmin, self.tz), num2date(dmax, self.tz)
  
      def viewlim_to_dt(self):
          """
          Converts the view interval to datetime objects.
          """
          vmin, vmax = self.axis.get_view_interval()
          if vmin > vmax:
              vmin, vmax = vmax, vmin
  
          return num2date(vmin, self.tz), num2date(vmax, self.tz)
  
      def _get_unit(self):
          """
          Return how many days a unit of the locator is; used for
          intelligent autoscaling.
          """
          return 1
  
      def _get_interval(self):
          """
          Return the number of units for each tick.
          """
          return 1
  
      def nonsingular(self, vmin, vmax):
          """
          Given the proposed upper and lower extent, adjust the range
          if it is too close to being singular (i.e. a range of ~0).
  
          """
          unit = self._get_unit()
          interval = self._get_interval()
          if abs(vmax - vmin) < 1e-6:
              vmin -= 2 * unit * interval
              vmax += 2 * unit * interval
          return vmin, vmax
  
  
  class RRuleLocator(DateLocator):
      # use the dateutil rrule instance
  
      def __init__(self, o, tz=None):
          DateLocator.__init__(self, tz)
          self.rule = o
  
      def __call__(self):
          # if no data have been set, this will tank with a ValueError
          try:
              dmin, dmax = self.viewlim_to_dt()
          except ValueError:
              return []
  
          return self.tick_values(dmin, dmax)
  
      def tick_values(self, vmin, vmax):
          delta = relativedelta(vmax, vmin)
  
          # We need to cap at the endpoints of valid datetime
          try:
              start = vmin - delta
          except ValueError:
              start = _from_ordinalf(1.0)
  
          try:
              stop = vmax + delta
          except ValueError:
              # The magic number!
              stop = _from_ordinalf(3652059.9999999)
  
          self.rule.set(dtstart=start, until=stop)
  
          dates = self.rule.between(vmin, vmax, True)
          if len(dates) == 0:
              return date2num([vmin, vmax])
          return self.raise_if_exceeds(date2num(dates))
  
      def _get_unit(self):
          """
          Return how many days a unit of the locator is; used for
          intelligent autoscaling.
          """
          freq = self.rule._rrule._freq
          return self.get_unit_generic(freq)
  
      @staticmethod
      def get_unit_generic(freq):
          if freq == YEARLY:
              return DAYS_PER_YEAR
          elif freq == MONTHLY:
              return DAYS_PER_MONTH
          elif freq == WEEKLY:
              return DAYS_PER_WEEK
          elif freq == DAILY:
              return 1.0
          elif freq == HOURLY:
              return 1.0 / HOURS_PER_DAY
          elif freq == MINUTELY:
              return 1.0 / MINUTES_PER_DAY
          elif freq == SECONDLY:
              return 1.0 / SEC_PER_DAY
          else:
              # error
              return -1   # or should this just return '1'?
  
      def _get_interval(self):
          return self.rule._rrule._interval
  
      def autoscale(self):
          """
          Set the view limits to include the data range.
          """
          dmin, dmax = self.datalim_to_dt()
          delta = relativedelta(dmax, dmin)
  
          # We need to cap at the endpoints of valid datetime
          try:
              start = dmin - delta
          except ValueError:
              start = _from_ordinalf(1.0)
  
          try:
              stop = dmax + delta
          except ValueError:
              # The magic number!
              stop = _from_ordinalf(3652059.9999999)
  
          self.rule.set(dtstart=start, until=stop)
          dmin, dmax = self.datalim_to_dt()
  
          vmin = self.rule.before(dmin, True)
          if not vmin:
              vmin = dmin
  
          vmax = self.rule.after(dmax, True)
          if not vmax:
              vmax = dmax
  
          vmin = date2num(vmin)
          vmax = date2num(vmax)
  
          return self.nonsingular(vmin, vmax)
  
  
  class AutoDateLocator(DateLocator):
      """
      On autoscale, this class picks the best
      :class:`DateLocator` to set the view limits and the tick
      locations.
      """
      def __init__(self, tz=None, minticks=5, maxticks=None,
                   interval_multiples=False):
          """
          *minticks* is the minimum number of ticks desired, which is used to
          select the type of ticking (yearly, monthly, etc.).
  
          *maxticks* is the maximum number of ticks desired, which controls
          any interval between ticks (ticking every other, every 3, etc.).
          For really fine-grained control, this can be a dictionary mapping
          individual rrule frequency constants (YEARLY, MONTHLY, etc.)
          to their own maximum number of ticks.  This can be used to keep
          the number of ticks appropriate to the format chosen in
          :class:`AutoDateFormatter`. Any frequency not specified in this
          dictionary is given a default value.
  
          *tz* is a :class:`tzinfo` instance.
  
          *interval_multiples* is a boolean that indicates whether ticks
          should be chosen to be multiple of the interval. This will lock
          ticks to 'nicer' locations. For example, this will force the
          ticks to be at hours 0,6,12,18 when hourly ticking is done at
          6 hour intervals.
  
          The AutoDateLocator has an interval dictionary that maps the
          frequency of the tick (a constant from dateutil.rrule) and a
          multiple allowed for that ticking.  The default looks like this::
  
            self.intervald = {
              YEARLY  : [1, 2, 4, 5, 10, 20, 40, 50, 100, 200, 400, 500,
                        1000, 2000, 4000, 5000, 10000],
              MONTHLY : [1, 2, 3, 4, 6],
              DAILY   : [1, 2, 3, 7, 14],
              HOURLY  : [1, 2, 3, 4, 6, 12],
              MINUTELY: [1, 5, 10, 15, 30],
              SECONDLY: [1, 5, 10, 15, 30],
              MICROSECONDLY: [1, 2, 5, 10, 20, 50, 100, 200, 500, 1000, 2000,
                             5000, 10000, 20000, 50000, 100000, 200000, 500000,
                             1000000],
              }
  
          The interval is used to specify multiples that are appropriate for
          the frequency of ticking. For instance, every 7 days is sensible
          for daily ticks, but for minutes/seconds, 15 or 30 make sense.
          You can customize this dictionary by doing::
  
            locator = AutoDateLocator()
            locator.intervald[HOURLY] = [3] # only show every 3 hours
          """
          DateLocator.__init__(self, tz)
          self._locator = YearLocator()
          self._freq = YEARLY
          self._freqs = [YEARLY, MONTHLY, DAILY, HOURLY, MINUTELY,
                         SECONDLY, MICROSECONDLY]
          self.minticks = minticks
  
          self.maxticks = {YEARLY: 11, MONTHLY: 12, DAILY: 11, HOURLY: 12,
                           MINUTELY: 11, SECONDLY: 11, MICROSECONDLY: 8}
          if maxticks is not None:
              try:
                  self.maxticks.update(maxticks)
              except TypeError:
                  # Assume we were given an integer. Use this as the maximum
                  # number of ticks for every frequency and create a
                  # dictionary for this
                  self.maxticks = dict(zip(self._freqs,
                                           [maxticks] * len(self._freqs)))
          self.interval_multiples = interval_multiples
          self.intervald = {
              YEARLY:   [1, 2, 4, 5, 10, 20, 40, 50, 100, 200, 400, 500,
                         1000, 2000, 4000, 5000, 10000],
              MONTHLY:  [1, 2, 3, 4, 6],
              DAILY:    [1, 2, 3, 7, 14, 21],
              HOURLY:   [1, 2, 3, 4, 6, 12],
              MINUTELY: [1, 5, 10, 15, 30],
              SECONDLY: [1, 5, 10, 15, 30],
              MICROSECONDLY: [1, 2, 5, 10, 20, 50, 100, 200, 500, 1000, 2000,
                              5000, 10000, 20000, 50000, 100000, 200000, 500000,
                              1000000]}
          self._byranges = [None, range(1, 13), range(1, 32),
                            range(0, 24), range(0, 60), range(0, 60), None]
  
      def __call__(self):
          'Return the locations of the ticks'
          self.refresh()
          return self._locator()
  
      def tick_values(self, vmin, vmax):
          return self.get_locator(vmin, vmax).tick_values(vmin, vmax)
  
      def nonsingular(self, vmin, vmax):
          # whatever is thrown at us, we can scale the unit.
          # But default nonsingular date plots at an ~4 year period.
          if vmin == vmax:
              vmin = vmin - DAYS_PER_YEAR * 2
              vmax = vmax + DAYS_PER_YEAR * 2
          return vmin, vmax
  
      def set_axis(self, axis):
          DateLocator.set_axis(self, axis)
          self._locator.set_axis(axis)
  
      def refresh(self):
          'Refresh internal information based on current limits.'
          dmin, dmax = self.viewlim_to_dt()
          self._locator = self.get_locator(dmin, dmax)
  
      def _get_unit(self):
          if self._freq in [MICROSECONDLY]:
              return 1. / MUSECONDS_PER_DAY
          else:
              return RRuleLocator.get_unit_generic(self._freq)
  
      def autoscale(self):
          'Try to choose the view limits intelligently.'
          dmin, dmax = self.datalim_to_dt()
          self._locator = self.get_locator(dmin, dmax)
          return self._locator.autoscale()
  
      def get_locator(self, dmin, dmax):
          'Pick the best locator based on a distance.'
          delta = relativedelta(dmax, dmin)
          tdelta = dmax - dmin
  
          # take absolute difference
          if dmin > dmax:
              delta = -delta
              tdelta = -tdelta
  
          # The following uses a mix of calls to relativedelta and timedelta
          # methods because there is incomplete overlap in the functionality of
          # these similar functions, and it's best to avoid doing our own math
          # whenever possible.
          numYears = float(delta.years)
          numMonths = (numYears * MONTHS_PER_YEAR) + delta.months
          numDays = tdelta.days   # Avoids estimates of days/month, days/year
          numHours = (numDays * HOURS_PER_DAY) + delta.hours
          numMinutes = (numHours * MIN_PER_HOUR) + delta.minutes
          numSeconds = np.floor(tdelta.total_seconds())
          numMicroseconds = np.floor(tdelta.total_seconds() * 1e6)
  
          nums = [numYears, numMonths, numDays, numHours, numMinutes,
                  numSeconds, numMicroseconds]
  
          use_rrule_locator = [True] * 6 + [False]
  
          # Default setting of bymonth, etc. to pass to rrule
          # [unused (for year), bymonth, bymonthday, byhour, byminute,
          #  bysecond, unused (for microseconds)]
          byranges = [None, 1, 1, 0, 0, 0, None]
  
          # Loop over all the frequencies and try to find one that gives at
          # least a minticks tick positions.  Once this is found, look for
          # an interval from an list specific to that frequency that gives no
          # more than maxticks tick positions. Also, set up some ranges
          # (bymonth, etc.) as appropriate to be passed to rrulewrapper.
          for i, (freq, num) in enumerate(zip(self._freqs, nums)):
              # If this particular frequency doesn't give enough ticks, continue
              if num < self.minticks:
                  # Since we're not using this particular frequency, set
                  # the corresponding by_ to None so the rrule can act as
                  # appropriate
                  byranges[i] = None
                  continue
  
              # Find the first available interval that doesn't give too many
              # ticks
              for interval in self.intervald[freq]:
                  if num <= interval * (self.maxticks[freq] - 1):
                      break
              else:
                  # We went through the whole loop without breaking, default to
                  # the last interval in the list and raise a warning
                  warnings.warn('AutoDateLocator was unable to pick an '
                                'appropriate interval for this date range. '
                                'It may be necessary to add an interval value '
                                "to the AutoDateLocator's intervald dictionary."
                                ' Defaulting to {0}.'.format(interval))
  
              # Set some parameters as appropriate
              self._freq = freq
  
              if self._byranges[i] and self.interval_multiples:
                  byranges[i] = self._byranges[i][::interval]
                  interval = 1
              else:
                  byranges[i] = self._byranges[i]
  
              # We found what frequency to use
              break
          else:
              raise ValueError('No sensible date limit could be found in the '
                               'AutoDateLocator.')
  
          if use_rrule_locator[i]:
              _, bymonth, bymonthday, byhour, byminute, bysecond, _ = byranges
  
              rrule = rrulewrapper(self._freq, interval=interval,
                                   dtstart=dmin, until=dmax,
                                   bymonth=bymonth, bymonthday=bymonthday,
                                   byhour=byhour, byminute=byminute,
                                   bysecond=bysecond)
  
              locator = RRuleLocator(rrule, self.tz)
          else:
              locator = MicrosecondLocator(interval, tz=self.tz)
  
          locator.set_axis(self.axis)
  
          locator.set_view_interval(*self.axis.get_view_interval())
          locator.set_data_interval(*self.axis.get_data_interval())
          return locator
  
  
  class YearLocator(DateLocator):
      """
      Make ticks on a given day of each year that is a multiple of base.
  
      Examples::
  
        # Tick every year on Jan 1st
        locator = YearLocator()
  
        # Tick every 5 years on July 4th
        locator = YearLocator(5, month=7, day=4)
      """
      def __init__(self, base=1, month=1, day=1, tz=None):
          """
          Mark years that are multiple of base on a given month and day
          (default jan 1).
          """
          DateLocator.__init__(self, tz)
          self.base = ticker.Base(base)
          self.replaced = {'month':  month,
                           'day':    day,
                           'hour':   0,
                           'minute': 0,
                           'second': 0,
                           'tzinfo': tz
                           }
  
      def __call__(self):
          # if no data have been set, this will tank with a ValueError
          try:
              dmin, dmax = self.viewlim_to_dt()
          except ValueError:
              return []
  
          return self.tick_values(dmin, dmax)
  
      def tick_values(self, vmin, vmax):
          ymin = self.base.le(vmin.year)
          ymax = self.base.ge(vmax.year)
  
          ticks = [vmin.replace(year=ymin, **self.replaced)]
          while 1:
              dt = ticks[-1]
              if dt.year >= ymax:
                  return date2num(ticks)
              year = dt.year + self.base.get_base()
              ticks.append(dt.replace(year=year, **self.replaced))
  
      def autoscale(self):
          """
          Set the view limits to include the data range.
          """
          dmin, dmax = self.datalim_to_dt()
  
          ymin = self.base.le(dmin.year)
          ymax = self.base.ge(dmax.year)
          vmin = dmin.replace(year=ymin, **self.replaced)
          vmax = dmax.replace(year=ymax, **self.replaced)
  
          vmin = date2num(vmin)
          vmax = date2num(vmax)
          return self.nonsingular(vmin, vmax)
  
  
  class MonthLocator(RRuleLocator):
      """
      Make ticks on occurances of each month month, e.g., 1, 3, 12.
      """
      def __init__(self, bymonth=None, bymonthday=1, interval=1, tz=None):
          """
          Mark every month in *bymonth*; *bymonth* can be an int or
          sequence.  Default is ``range(1,13)``, i.e. every month.
  
          *interval* is the interval between each iteration.  For
          example, if ``interval=2``, mark every second occurance.
          """
          if bymonth is None:
              bymonth = range(1, 13)
          elif isinstance(bymonth, np.ndarray):
              # This fixes a bug in dateutil <= 2.3 which prevents the use of
              # numpy arrays in (among other things) the bymonthday, byweekday
              # and bymonth parameters.
              bymonth = [x.item() for x in bymonth.astype(int)]
  
          rule = rrulewrapper(MONTHLY, bymonth=bymonth, bymonthday=bymonthday,
                           interval=interval, **self.hms0d)
          RRuleLocator.__init__(self, rule, tz)
  
  
  class WeekdayLocator(RRuleLocator):
      """
      Make ticks on occurances of each weekday.
      """
  
      def __init__(self, byweekday=1, interval=1, tz=None):
          """
          Mark every weekday in *byweekday*; *byweekday* can be a number or
          sequence.
  
          Elements of *byweekday* must be one of MO, TU, WE, TH, FR, SA,
          SU, the constants from :mod:`dateutil.rrule`, which have been
          imported into the :mod:`matplotlib.dates` namespace.
  
          *interval* specifies the number of weeks to skip.  For example,
          ``interval=2`` plots every second week.
          """
          if isinstance(byweekday, np.ndarray):
              # This fixes a bug in dateutil <= 2.3 which prevents the use of
              # numpy arrays in (among other things) the bymonthday, byweekday
              # and bymonth parameters.
              [x.item() for x in byweekday.astype(int)]
  
          rule = rrulewrapper(DAILY, byweekday=byweekday,
                              interval=interval, **self.hms0d)
          RRuleLocator.__init__(self, rule, tz)
  
  
  class DayLocator(RRuleLocator):
      """
      Make ticks on occurances of each day of the month.  For example,
      1, 15, 30.
      """
      def __init__(self, bymonthday=None, interval=1, tz=None):
          """
          Mark every day in *bymonthday*; *bymonthday* can be an int or
          sequence.
  
          Default is to tick every day of the month: ``bymonthday=range(1,32)``
          """
          if not interval == int(interval) or interval < 1:
              raise ValueError("interval must be an integer greater than 0")
          if bymonthday is None:
              bymonthday = range(1, 32)
          elif isinstance(bymonthday, np.ndarray):
              # This fixes a bug in dateutil <= 2.3 which prevents the use of
              # numpy arrays in (among other things) the bymonthday, byweekday
              # and bymonth parameters.
              bymonthday = [x.item() for x in bymonthday.astype(int)]
  
          rule = rrulewrapper(DAILY, bymonthday=bymonthday,
                              interval=interval, **self.hms0d)
          RRuleLocator.__init__(self, rule, tz)
  
  
  class HourLocator(RRuleLocator):
      """
      Make ticks on occurances of each hour.
      """
      def __init__(self, byhour=None, interval=1, tz=None):
          """
          Mark every hour in *byhour*; *byhour* can be an int or sequence.
          Default is to tick every hour: ``byhour=range(24)``
  
          *interval* is the interval between each iteration.  For
          example, if ``interval=2``, mark every second occurrence.
          """
          if byhour is None:
              byhour = range(24)
  
          rule = rrulewrapper(HOURLY, byhour=byhour, interval=interval,
                              byminute=0, bysecond=0)
          RRuleLocator.__init__(self, rule, tz)
  
  
  class MinuteLocator(RRuleLocator):
      """
      Make ticks on occurances of each minute.
      """
      def __init__(self, byminute=None, interval=1, tz=None):
          """
          Mark every minute in *byminute*; *byminute* can be an int or
          sequence.  Default is to tick every minute: ``byminute=range(60)``
  
          *interval* is the interval between each iteration.  For
          example, if ``interval=2``, mark every second occurrence.
          """
          if byminute is None:
              byminute = range(60)
  
          rule = rrulewrapper(MINUTELY, byminute=byminute, interval=interval,
                              bysecond=0)
          RRuleLocator.__init__(self, rule, tz)
  
  
  class SecondLocator(RRuleLocator):
      """
      Make ticks on occurances of each second.
      """
      def __init__(self, bysecond=None, interval=1, tz=None):
          """
          Mark every second in *bysecond*; *bysecond* can be an int or
          sequence.  Default is to tick every second: ``bysecond = range(60)``
  
          *interval* is the interval between each iteration.  For
          example, if ``interval=2``, mark every second occurrence.
  
          """
          if bysecond is None:
              bysecond = range(60)
  
          rule = rrulewrapper(SECONDLY, bysecond=bysecond, interval=interval)
          RRuleLocator.__init__(self, rule, tz)
  
  
  class MicrosecondLocator(DateLocator):
      """
      Make ticks on occurances of each microsecond.
  
      """
      def __init__(self, interval=1, tz=None):
          """
          *interval* is the interval between each iteration.  For
          example, if ``interval=2``, mark every second microsecond.
  
          """
          self._interval = interval
          self._wrapped_locator = ticker.MultipleLocator(interval)
          self.tz = tz
  
      def set_axis(self, axis):
          self._wrapped_locator.set_axis(axis)
          return DateLocator.set_axis(self, axis)
  
      def set_view_interval(self, vmin, vmax):
          self._wrapped_locator.set_view_interval(vmin, vmax)
          return DateLocator.set_view_interval(self, vmin, vmax)
  
      def set_data_interval(self, vmin, vmax):
          self._wrapped_locator.set_data_interval(vmin, vmax)
          return DateLocator.set_data_interval(self, vmin, vmax)
  
      def __call__(self):
          # if no data have been set, this will tank with a ValueError
          try:
              dmin, dmax = self.viewlim_to_dt()
          except ValueError:
              return []
  
          return self.tick_values(dmin, dmax)
  
      def tick_values(self, vmin, vmax):
          nmin, nmax = date2num((vmin, vmax))
          nmin *= MUSECONDS_PER_DAY
          nmax *= MUSECONDS_PER_DAY
          ticks = self._wrapped_locator.tick_values(nmin, nmax)
          ticks = [tick / MUSECONDS_PER_DAY for tick in ticks]
          return ticks
  
      def _get_unit(self):
          """
          Return how many days a unit of the locator is; used for
          intelligent autoscaling.
          """
          return 1. / MUSECONDS_PER_DAY
  
      def _get_interval(self):
          """
          Return the number of units for each tick.
          """
          return self._interval
  
  
  def _close_to_dt(d1, d2, epsilon=5):
      """
      Assert that datetimes *d1* and *d2* are within *epsilon* microseconds.
      """
      delta = d2 - d1
      mus = abs(delta.total_seconds() * 1e6)
      assert mus < epsilon
  
  
  def _close_to_num(o1, o2, epsilon=5):
      """
      Assert that float ordinals *o1* and *o2* are within *epsilon*
      microseconds.
      """
      delta = abs((o2 - o1) * MUSECONDS_PER_DAY)
      assert delta < epsilon
  
  
  def epoch2num(e):
      """
      Convert an epoch or sequence of epochs to the new date format,
      that is days since 0001.
      """
      return EPOCH_OFFSET + np.asarray(e) / SEC_PER_DAY
  
  
  def num2epoch(d):
      """
      Convert days since 0001 to epoch.  *d* can be a number or sequence.
      """
      return (np.asarray(d) - EPOCH_OFFSET) * SEC_PER_DAY
  
  
  def mx2num(mxdates):
      """
      Convert mx :class:`datetime` instance (or sequence of mx
      instances) to the new date format.
      """
      scalar = False
      if not cbook.iterable(mxdates):
          scalar = True
          mxdates = [mxdates]
      ret = epoch2num([m.ticks() for m in mxdates])
      if scalar:
          return ret[0]
      else:
          return ret
  
  
  def date_ticker_factory(span, tz=None, numticks=5):
      """
      Create a date locator with *numticks* (approx) and a date formatter
      for *span* in days.  Return value is (locator, formatter).
      """
  
      if span == 0:
          span = 1 / HOURS_PER_DAY
  
      mins = span * MINUTES_PER_DAY
      hrs = span * HOURS_PER_DAY
      days = span
      wks = span / DAYS_PER_WEEK
      months = span / DAYS_PER_MONTH      # Approx
      years = span / DAYS_PER_YEAR        # Approx
  
      if years > numticks:
          locator = YearLocator(int(years / numticks), tz=tz)  # define
          fmt = '%Y'
      elif months > numticks:
          locator = MonthLocator(tz=tz)
          fmt = '%b %Y'
      elif wks > numticks:
          locator = WeekdayLocator(tz=tz)
          fmt = '%a, %b %d'
      elif days > numticks:
          locator = DayLocator(interval=int(math.ceil(days / numticks)), tz=tz)
          fmt = '%b %d'
      elif hrs > numticks:
          locator = HourLocator(interval=int(math.ceil(hrs / numticks)), tz=tz)
          fmt = '%H:%M\n%b %d'
      elif mins > numticks:
          locator = MinuteLocator(interval=int(math.ceil(mins / numticks)),
                                  tz=tz)
          fmt = '%H:%M:%S'
      else:
          locator = MinuteLocator(tz=tz)
          fmt = '%H:%M:%S'
  
      formatter = DateFormatter(fmt, tz=tz)
      return locator, formatter
  
  
  def seconds(s):
      """
      Return seconds as days.
      """
      return float(s) / SEC_PER_DAY
  
  
  def minutes(m):
      """
      Return minutes as days.
      """
      return float(m) / MINUTES_PER_DAY
  
  
  def hours(h):
      """
      Return hours as days.
      """
      return h / HOURS_PER_DAY
  
  
  def weeks(w):
      """
      Return weeks as days.
      """
      return w * DAYS_PER_WEEK
  
  
  class DateConverter(units.ConversionInterface):
      """
      Converter for datetime.date and datetime.datetime data,
      or for date/time data represented as it would be converted
      by :func:`date2num`.
  
      The 'unit' tag for such data is None or a tzinfo instance.
      """
  
      @staticmethod
      def axisinfo(unit, axis):
          """
          Return the :class:`~matplotlib.units.AxisInfo` for *unit*.
  
          *unit* is a tzinfo instance or None.
          The *axis* argument is required but not used.
          """
          tz = unit
  
          majloc = AutoDateLocator(tz=tz)
          majfmt = AutoDateFormatter(majloc, tz=tz)
          datemin = datetime.date(2000, 1, 1)
          datemax = datetime.date(2010, 1, 1)
  
          return units.AxisInfo(majloc=majloc, majfmt=majfmt, label='',
                                default_limits=(datemin, datemax))
  
      @staticmethod
      def convert(value, unit, axis):
          """
          If *value* is not already a number or sequence of numbers,
          convert it with :func:`date2num`.
  
          The *unit* and *axis* arguments are not used.
          """
          if units.ConversionInterface.is_numlike(value):
              return value
          return date2num(value)
  
      @staticmethod
      def default_units(x, axis):
          """
          Return the tzinfo instance of *x* or of its first element, or None
          """
          if isinstance(x, np.ndarray):
              x = x.ravel()
  
          try:
              x = cbook.safe_first_element(x)
          except (TypeError, StopIteration):
              pass
  
          try:
              return x.tzinfo
          except AttributeError:
              pass
          return None
  
  
  units.registry[datetime.date] = DateConverter()
  units.registry[datetime.datetime] = DateConverter()
  