Add month names

Fix localiztion of months

Add series test and whatsnew notes

Modify test and lint

Add Timestamp rst

Address comments

Lint, move whatsnew, remove hardcoded Monday, check that get_locale is None

create functions instead of attributes

Fix white space

Modify tests

Lint

Rebase and add depreciation message

Deprecate weekday_name, create localizing function in ccalendar.pyx

clean up imports

Address user comments

Try to address ci issues

Rebase and adjust tests

Move some imports to top of file, remove dup implimention of day_name in fields

Fix failing test

allow path to accept weekday_name as well

address review

address review missed files

fix typo and call internal method

Fix lint

modify pytest param for appvoyer

fix more appvoyer tests

Remove weekday_name availability

Author: mroeschke

Diff for: doc/source/api.rst

@@ -551,7 +551,6 @@ These can be accessed like ``Series.dt.<property>``.
    Series.dt.weekofyear
    Series.dt.dayofweek
    Series.dt.weekday
-   Series.dt.weekday_name
    Series.dt.dayofyear
    Series.dt.quarter
    Series.dt.is_month_start
@@ -581,6 +580,8 @@ These can be accessed like ``Series.dt.<property>``.
    Series.dt.round
    Series.dt.floor
    Series.dt.ceil
+   Series.dt.month_name
+   Series.dt.day_name
 
 **Timedelta Properties**
 
@@ -1723,7 +1724,6 @@ Time/Date Components
    DatetimeIndex.week
    DatetimeIndex.dayofweek
    DatetimeIndex.weekday
-   DatetimeIndex.weekday_name
    DatetimeIndex.quarter
    DatetimeIndex.tz
    DatetimeIndex.freq
@@ -1759,6 +1759,8 @@ Time-specific operations
    DatetimeIndex.round
    DatetimeIndex.floor
    DatetimeIndex.ceil
+   DatetimeIndex.month_name
+   DatetimeIndex.day_name
 
 Conversion
 ~~~~~~~~~~
@@ -1940,7 +1942,6 @@ Properties
     Timestamp.tzinfo
     Timestamp.value
     Timestamp.week
-    Timestamp.weekday_name
     Timestamp.weekofyear
     Timestamp.year
 
@@ -1954,6 +1955,7 @@ Methods
     Timestamp.combine
     Timestamp.ctime
     Timestamp.date
+    Timestamp.day_name
     Timestamp.dst
     Timestamp.floor
     Timestamp.freq
@@ -1963,6 +1965,7 @@ Methods
     Timestamp.isocalendar
     Timestamp.isoformat
     Timestamp.isoweekday
+    Timestamp.month_name
     Timestamp.normalize
     Timestamp.now
     Timestamp.replace

Diff for: doc/source/whatsnew/v0.23.0.txt

@@ -338,7 +338,8 @@ Other Enhancements
 - For subclassed ``DataFrames``, :func:`DataFrame.apply` will now preserve the ``Series`` subclass (if defined) when passing the data to the applied function (:issue:`19822`)
 - :func:`DataFrame.from_dict` now accepts a ``columns`` argument that can be used to specify the column names when ``orient='index'`` is used (:issue:`18529`)
 - Added option ``display.html.use_mathjax`` so `MathJax <https://www.mathjax.org/>`_ can be disabled when rendering tables in ``Jupyter`` notebooks (:issue:`19856`, :issue:`19824`)
-
+- :meth:`Timestamp.month_name`, :meth:`DatetimeIndex.month_name`, and :meth:`Series.dt.month_name` are now available (:issue:`12805`)
+- :meth:`Timestamp.day_name` and :meth:`DatetimeIndex.day_name` are now available to return day names with a specified locale (:issue:`12806`)
 
 .. _whatsnew_0230.api_breaking:
 
@@ -677,6 +678,7 @@ Deprecations
 - The ``broadcast`` parameter of ``.apply()`` is deprecated in favor of ``result_type='broadcast'`` (:issue:`18577`)
 - The ``reduce`` parameter of ``.apply()`` is deprecated in favor of ``result_type='reduce'`` (:issue:`18577`)
 - The ``order`` parameter of :func:`factorize` is deprecated and will be removed in a future release (:issue:`19727`)
+- :attr:`Timestamp.weekday_name`, :attr:`DatetimeIndex.weekday_name`, and :attr:`Series.dt.weekday_name` are deprecated in favor of :meth:`Timestamp.day_name`, :meth:`DatetimeIndex.day_name`, and :meth:`Series.dt.day_name` (:issue:`12806`)
 
 .. _whatsnew_0230.prior_deprecations:
 

Diff for: pandas/_libs/tslibs/ccalendar.pyx

@@ -12,6 +12,8 @@ cimport numpy as cnp
 from numpy cimport int64_t, int32_t
 cnp.import_array()
 
+from locale import LC_TIME
+from strptime import LocaleTime
 
 # ----------------------------------------------------------------------
 # Constants
@@ -35,11 +37,18 @@ cdef int32_t* _month_offset = [
 # Canonical location for other modules to find name constants
 MONTHS = ['JAN', 'FEB', 'MAR', 'APR', 'MAY', 'JUN', 'JUL',
           'AUG', 'SEP', 'OCT', 'NOV', 'DEC']
+# The first blank line is consistent with calendar.month_name in the calendar
+# standard library
+MONTHS_FULL = ['', 'January', 'February', 'March', 'April', 'May', 'June',
+               'July', 'August', 'September', 'October', 'November',
+               'December']
 MONTH_NUMBERS = {name: num for num, name in enumerate(MONTHS)}
 MONTH_ALIASES = {(num + 1): name for num, name in enumerate(MONTHS)}
 MONTH_TO_CAL_NUM = {name: num + 1 for num, name in enumerate(MONTHS)}
 
 DAYS = ['MON', 'TUE', 'WED', 'THU', 'FRI', 'SAT', 'SUN']
+DAYS_FULL = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday',
+             'Saturday', 'Sunday']
 int_to_weekday = {num: name for num, name in enumerate(DAYS)}
 weekday_to_int = {int_to_weekday[key]: key for key in int_to_weekday}
 
@@ -199,3 +208,23 @@ cpdef int32_t get_day_of_year(int year, int month, int day) nogil:
 
     day_of_year = mo_off + day
     return day_of_year
+
+
+cpdef get_locale_names(object name_type, object locale=None):
+    """Returns an array of localized day or month names
+
+    Parameters
+    ----------
+    name_type : string, attribute of LocaleTime() in which to return localized
+        names
+    locale : string
+
+    Returns
+    -------
+    list of locale names
+
+    """
+    from pandas.util.testing import set_locale
+
+    with set_locale(locale, LC_TIME):
+        return getattr(LocaleTime(), name_type)

Diff for: pandas/_libs/tslibs/fields.pyx

@@ -13,7 +13,7 @@ cimport numpy as cnp
 from numpy cimport ndarray, int64_t, int32_t, int8_t
 cnp.import_array()
 
-
+from ccalendar import get_locale_names, MONTHS_FULL, DAYS_FULL
 from ccalendar cimport (get_days_in_month, is_leapyear, dayofweek,
                         get_week_of_year, get_day_of_year)
 from np_datetime cimport (pandas_datetimestruct, pandas_timedeltastruct,
@@ -85,34 +85,49 @@ def build_field_sarray(ndarray[int64_t] dtindex):
 
 @cython.wraparound(False)
 @cython.boundscheck(False)
-def get_date_name_field(ndarray[int64_t] dtindex, object field):
+def get_date_name_field(ndarray[int64_t] dtindex, object field,
+                        object locale=None):
     """
     Given a int64-based datetime index, return array of strings of date
     name based on requested field (e.g. weekday_name)
     """
     cdef:
         Py_ssize_t i, count = 0
-        ndarray[object] out
+        ndarray[object] out, names
         pandas_datetimestruct dts
         int dow
 
-    _dayname = np.array(
-        ['Monday', 'Tuesday', 'Wednesday', 'Thursday',
-            'Friday', 'Saturday', 'Sunday'],
-        dtype=np.object_)
-
     count = len(dtindex)
     out = np.empty(count, dtype=object)
 
-    if field == 'weekday_name':
+    if field == 'day_name' or field == 'weekday_name':
+        if locale is None:
+            names = np.array(DAYS_FULL, dtype=np.object_)
+        else:
+            names = np.array(get_locale_names('f_weekday', locale),
+                             dtype=np.object_)
         for i in range(count):
             if dtindex[i] == NPY_NAT:
                 out[i] = np.nan
                 continue
 
             dt64_to_dtstruct(dtindex[i], &dts)
             dow = dayofweek(dts.year, dts.month, dts.day)
-            out[i] = _dayname[dow]
+            out[i] = names[dow].capitalize()
+        return out
+    elif field == 'month_name':
+        if locale is None:
+            names = np.array(MONTHS_FULL, dtype=np.object_)
+        else:
+            names = np.array(get_locale_names('f_month', locale),
+                             dtype=np.object_)
+        for i in range(count):
+            if dtindex[i] == NPY_NAT:
+                out[i] = np.nan
+                continue
+
+            dt64_to_dtstruct(dtindex[i], &dts)
+            out[i] = names[dts.month].capitalize()
         return out
 
     raise ValueError("Field %s not supported" % field)

Diff for: pandas/_libs/tslibs/nattype.pyx

@@ -1,6 +1,5 @@
 # -*- coding: utf-8 -*-
 # cython: profile=False
-import warnings
 
 from cpython cimport (
     PyFloat_Check, PyComplex_Check,
@@ -39,24 +38,19 @@ _nat_scalar_rules[Py_GE] = False
 # ----------------------------------------------------------------------
 
 
-def _make_nan_func(func_name, cls):
+def _make_nan_func(func_name, doc):
     def f(*args, **kwargs):
         return np.nan
     f.__name__ = func_name
-    f.__doc__ = getattr(cls, func_name).__doc__
+    f.__doc__ = doc
     return f
 
 
-def _make_nat_func(func_name, cls):
+def _make_nat_func(func_name, doc):
     def f(*args, **kwargs):
         return NaT
-
     f.__name__ = func_name
-    if isinstance(cls, str):
-        # passed the literal docstring directly
-        f.__doc__ = cls
-    else:
-        f.__doc__ = getattr(cls, func_name).__doc__
+    f.__doc__ = doc
     return f
 
 
@@ -318,11 +312,40 @@ class NaTType(_NaT):
     # These are the ones that can get their docstrings from datetime.
 
     # nan methods
-    weekday = _make_nan_func('weekday', datetime)
-    isoweekday = _make_nan_func('isoweekday', datetime)
+    weekday = _make_nan_func('weekday', datetime.weekday.__doc__)
+    isoweekday = _make_nan_func('isoweekday', datetime.isoweekday.__doc__)
+    month_name = _make_nan_func('month_name',  # noqa:E128
+        """
+        Return the month name of the Timestamp with specified locale.
+
+        Parameters
+        ----------
+        locale : string, default None (English locale)
+            locale determining the language in which to return the month name
+
+        Returns
+        -------
+        month_name : string
+
+        .. versionadded:: 0.23.0
+        """)
+    day_name = _make_nan_func('day_name', # noqa:E128
+        """
+        Return the day name of the Timestamp with specified locale.
 
+        Parameters
+        ----------
+        locale : string, default None (English locale)
+            locale determining the language in which to return the day name
+
+        Returns
+        -------
+        day_name : string
+
+        .. versionadded:: 0.23.0
+        """)
     # _nat_methods
-    date = _make_nat_func('date', datetime)
+    date = _make_nat_func('date', datetime.date.__doc__)
 
     utctimetuple = _make_error_func('utctimetuple', datetime)
     timetz = _make_error_func('timetz', datetime)

Diff for: pandas/_libs/tslibs/timestamps.pyx

@@ -24,7 +24,7 @@ cimport ccalendar
 from conversion import tz_localize_to_utc, date_normalize
 from conversion cimport (tz_convert_single, _TSObject,
                          convert_to_tsobject, convert_datetime_to_tsobject)
-from fields import get_date_field, get_start_end_field
+from fields import get_start_end_field, get_date_name_field
 from nattype import NaT
 from nattype cimport NPY_NAT
 from np_datetime import OutOfBoundsDatetime
@@ -352,6 +352,16 @@ cdef class _Timestamp(datetime):
                                   field, freqstr, month_kw)
         return out[0]
 
+    cpdef _get_date_name_field(self, object field, object locale):
+        cdef:
+            int64_t val
+            ndarray out
+
+        val = self._maybe_convert_value_to_local()
+        out = get_date_name_field(np.array([val], dtype=np.int64),
+                                  field, locale=locale)
+        return out[0]
+
     @property
     def _repr_base(self):
         return '{date} {time}'.format(date=self._date_repr,
@@ -714,12 +724,50 @@ class Timestamp(_Timestamp):
     def dayofweek(self):
         return self.weekday()
 
+    def day_name(self, locale=None):
+        """
+        Return the day name of the Timestamp with specified locale.
+
+        Parameters
+        ----------
+        locale : string, default None (English locale)
+            locale determining the language in which to return the day name
+
+        Returns
+        -------
+        day_name : string
+
+        .. versionadded:: 0.23.0
+        """
+        return self._get_date_name_field('day_name', locale)
+
+    def month_name(self, locale=None):
+        """
+        Return the month name of the Timestamp with specified locale.
+
+        Parameters
+        ----------
+        locale : string, default None (English locale)
+            locale determining the language in which to return the month name
+
+        Returns
+        -------
+        month_name : string
+
+        .. versionadded:: 0.23.0
+        """
+        return self._get_date_name_field('month_name', locale)
+
     @property
     def weekday_name(self):
-        cdef dict wdays = {0: 'Monday', 1: 'Tuesday', 2: 'Wednesday',
-                           3: 'Thursday', 4: 'Friday', 5: 'Saturday',
-                           6: 'Sunday'}
-        return wdays[self.weekday()]
+        """
+        .. deprecated:: 0.23.0
+            Use ``Timestamp.day_name()`` instead
+        """
+        warnings.warn("`weekday_name` is deprecated and will be removed in a "
+                      "future version. Use `day_name` instead",
+                      DeprecationWarning)
+        return self.day_name()
 
     @property
     def dayofyear(self):