Support CLDR 48 relative date formats

babel/core.py

@@ -1000,6 +1000,22 @@ def datetime_formats(self) -> localedata.LocaleDataDict:
         """
         return self._data['datetime_formats']
 
+    @property
+    def datetime_formats_relative(self) -> localedata.LocaleDataDict:
+        """Locale patterns for combining a relative date with a time.
+
+        Introduced in CLDR 48.
+
+        .. note:: The format of the value returned may change between
+                  Babel versions.
+
+        >>> Locale('en').datetime_formats_relative['full']
+        "{1} 'at' {0}"
+
+        .. versionadded:: 2.19
+        """
+        return self._data['datetime_formats_relative']
+
     @property
     def datetime_skeletons(self) -> localedata.LocaleDataDict:
         """Locale patterns for formatting parts of a datetime.

babel/dates.py

@@ -355,6 +355,57 @@ def get_era_names(
     return Locale.parse(locale or LC_TIME).eras[width]
 
 
+def get_relative_name(
+    field: str,
+    offset: int,
+    length: Literal['long', 'short', 'narrow'] = 'long',
+    locale: Locale | str | None = None,
+) -> str | None:
+    """Return the locale's literal name for a relative offset of a date field.
+
+    These are the CLDR ``<relative>`` strings such as "yesterday", "today",
+    "tomorrow" for ``field='day'``, or "last Monday"/"this Monday"/"next Monday"
+    for ``field='mon'``.
+
+    Returns ``None`` when the locale does not define a literal name for the
+    requested field/offset (in which case a phrase like "in 2 days" built
+    via :func:`format_timedelta` is typically the right fallback).
+
+    >>> get_relative_name('day', -1, locale='en')
+    'yesterday'
+    >>> get_relative_name('day', 1, locale='en')
+    'tomorrow'
+    >>> get_relative_name('day', -2, locale='de')
+    'vorgestern'
+    >>> get_relative_name('year', 1, locale='en')
+    'next year'
+    >>> get_relative_name('year', 1, length='short', locale='en')
+    'next yr.'
+    >>> get_relative_name('mon', 1, locale='en')
+    'next Monday'
+
+    Offsets without a literal name return ``None``:
+
+    >>> get_relative_name('day', 5, locale='en') is None
+    True
+
+    :param field: the date field, e.g. "day", "week", "month", "year",
+                  "hour", "minute", "second", "quarter", or a weekday
+                  abbreviation like "mon", "tue", etc.
+    :param offset: the offset from the current value of *field*.
+    :param length: "long", "short", or "narrow".
+    :param locale: a `Locale` object or a locale identifier.  Defaults to the
+                   system time locale.
+
+    .. versionadded:: 2.19
+    """
+    locale = Locale.parse(locale or LC_TIME)
+    date_fields = locale._data['date_fields']
+    key = field if length == 'long' else f'{field}-{length}'
+    data = date_fields.get(key) or date_fields.get(field) or {}
+    return data.get('relative', {}).get(offset)
+
+
 def get_date_format(
     format: _PredefinedTimeFormat = 'medium',
     locale: Locale | str | None = None,
@@ -764,6 +815,58 @@ def format_datetime(
         return parse_pattern(format).apply(datetime, locale)
 
 
+def format_relative_datetime(
+    relative_date: str,
+    time: datetime.time | datetime.datetime | float | None = None,
+    format: _PredefinedTimeFormat = 'medium',
+    tzinfo: datetime.tzinfo | None = None,
+    locale: Locale | str | None = None,
+) -> str:
+    """Combine a pre-formatted relative date with a time using the locale's
+    relative datetime pattern.
+
+    For instance, in English you might say "tomorrow at 3:30 PM" instead of
+    "tomorrow, 3:30 PM".
+
+    The caller supplies the relative date portion as a string
+    (such as "tomorrow" or "in 3 days"); this function formats the time and joins the two.
+
+    >>> from datetime import time
+    >>> format_relative_datetime('tomorrow', time(15, 30), locale='en', format='long')
+    'tomorrow at 3:30:00\u202fPM UTC'
+    >>> format_relative_datetime('morgen', time(15, 30), locale='de', format='long')
+    'morgen um 15:30:00 UTC'
+
+    When the locale does not define a relative pattern for the requested
+    width, its standard datetime pattern is used, as CLDR's root locale
+    aliases ``relative`` patterns to ``standard`` ones:
+
+    >>> format_relative_datetime('zítra', time(15, 30), locale='cs', format='short')
+    'zítra 15:30'
+
+    :param relative_date: the already-localized relative date string.
+    :param time: the time to combine with the relative date.
+                 If ``None`` the current time is used.
+    :param format: one of "full", "long", "medium", or "short".
+    :param tzinfo: the timezone to apply to the time for display.
+    :param locale: a `Locale` object or a locale identifier.
+                   Defaults to the system time locale.
+
+    .. versionadded:: 2.19
+    """
+    locale = Locale.parse(locale or LC_TIME)
+    pattern = (
+        locale.datetime_formats_relative.get(format)
+        or get_datetime_format(format, locale=locale)
+    )
+    return (
+        pattern
+        .replace("'", "")
+        .replace('{0}', format_time(time, format, tzinfo=tzinfo, locale=locale))
+        .replace('{1}', relative_date)
+    )
+
+
 def format_time(
     time: datetime.time | datetime.datetime | float | None = None,
     format: _PredefinedTimeFormat | str = 'medium',

docs/api/dates.rst

@@ -21,6 +21,8 @@ Date and Time Formatting
 
 .. autofunction:: format_interval(start, end, skeleton=None, tzinfo=None, fuzzy=True, locale=default_locale('LC_TIME'))
 
+.. autofunction:: format_relative_datetime
+
 Timezone Functionality
 ----------------------
 
@@ -59,6 +61,8 @@ Data Access
 
 .. autofunction:: get_time_format
 
+.. autofunction:: get_relative_name
+
 Basic Parsing
 -------------
 

scripts/import_cldr.py

@@ -764,6 +764,7 @@ def parse_calendar_time_formats(data, calendar):
 
 def parse_calendar_datetime_skeletons(data, calendar):
     datetime_formats = data.setdefault('datetime_formats', {})
+    datetime_formats_relative = data.setdefault('datetime_formats_relative', {})
     datetime_skeletons = data.setdefault('datetime_skeletons', {})
     for format in calendar.findall('dateTimeFormats'):
         for elem in format:
@@ -772,7 +773,15 @@ def parse_calendar_datetime_skeletons(data, calendar):
                 if _should_skip_elem(elem, type, datetime_formats):
                     continue
                 try:
-                    datetime_formats[type] = str(elem.findtext('dateTimeFormat/pattern'))
+                    for dtf in elem.findall('dateTimeFormat'):
+                        pattern_elem = dtf.find('pattern')
+                        if pattern_elem is None or pattern_elem.text is None:
+                            continue
+                        pattern = str(pattern_elem.text)
+                        if dtf.attrib.get('type') == 'relative':
+                            datetime_formats_relative[type] = pattern
+                        elif 'type' not in dtf.attrib:
+                            datetime_formats[type] = pattern
                 except ValueError as e:
                     log.error(e)
             elif elem.tag == 'alias':
@@ -1028,6 +1037,13 @@ def parse_date_fields(data, tree):
             for pattern in rel_time.findall('relativeTimePattern'):
                 type_dict = date_fields[field_type].setdefault(rel_time_type, {})
                 type_dict[pattern.attrib['count']] = str(pattern.text)
+        # Literal names for specific offsets, e.g. <relative type="-1">yesterday</relative>.
+        for rel in elem.findall('relative'):
+            if rel.text is None:
+                continue
+            offset = int(rel.attrib['type'])
+            names = date_fields[field_type].setdefault('relative', {})
+            names[offset] = str(rel.text)
 
 
 def parse_interval_formats(data, tree):

tests/test_dates.py

@@ -424,6 +424,169 @@ def test_format_datetime(timezone_getter):
     assert custom == '2007.04.01 AD at 11:30:00 EDT'
 
 
+def test_get_relative_name():
+    assert dates.get_relative_name('day', -1, locale='en') == 'yesterday'
+    assert dates.get_relative_name('day', 0, locale='en') == 'today'
+    assert dates.get_relative_name('day', 1, locale='en') == 'tomorrow'
+    # German has -2/+2 (vorgestern/übermorgen); English does not.
+    assert dates.get_relative_name('day', -2, locale='de') == 'vorgestern'
+    assert dates.get_relative_name('day', 2, locale='de') == 'übermorgen'
+    assert dates.get_relative_name('day', 2, locale='en') is None
+    # Length variants
+    assert dates.get_relative_name('year', 1, locale='en') == 'next year'
+    assert dates.get_relative_name('year', 1, length='short', locale='en') == 'next yr.'
+    # Weekday fields
+    assert dates.get_relative_name('mon', 1, locale='en') == 'next Monday'
+    # Unknown field returns None
+    assert dates.get_relative_name('bogus', 0, locale='en') is None
+
+
+def test_get_relative_name_pairs_with_format_relative_datetime():
+    # Composing the two APIs should produce a complete localized phrase.
+    relative = dates.get_relative_name('day', 1, locale='en')
+    assert dates.format_relative_datetime(
+        relative, time(15, 30), format='long', locale='en',
+    ) == 'tomorrow at 3:30:00\u202fPM UTC'
+
+
+@pytest.mark.parametrize(('field', 'offset', 'expected'), [
+    ('day', -2, 'toissa päivänä'),
+    ('day', -1, 'eilen'),
+    ('day', 0, 'tänään'),
+    ('day', 1, 'huomenna'),
+    ('day', 2, 'ylihuomenna'),
+    ('week', -1, 'viime viikolla'),
+    ('week', 1, 'ensi viikolla'),
+    ('month', 0, 'tässä kuussa'),
+    ('year', -1, 'viime vuonna'),
+    ('year', 1, 'ensi vuonna'),
+    ('second', 0, 'nyt'),
+    ('quarter', 1, 'ensi neljännesvuonna'),
+    ('mon', 1, 'ensi maanantaina'),
+    ('sun', -1, 'viime sunnuntaina'),
+])
+def test_get_relative_name_fi(field: str, offset: int, expected: str):
+    assert dates.get_relative_name(field, offset, locale='fi') == expected
+
+
+@pytest.mark.parametrize(('field', 'offset', 'length', 'expected'), [
+    ('day', -2, 'short', 'toissap.'),
+    ('day', 1, 'short', 'huom.'),
+    ('day', 2, 'short', 'ylihuom.'),
+    ('day', 1, 'narrow', 'huom.'),  # day-short, aliased from day-narrow
+])
+def test_get_relative_name_fi_lengths(field: str, offset: int, length: str, expected: str):
+    assert dates.get_relative_name(field, offset, length=length, locale='fi') == expected
+
+
+@pytest.mark.parametrize(('field', 'offset', 'length', 'expected'), [
+    # cs defines `year-short`, but with relativeTime patterns only. (no <relative> names),
+    # # so these fall through to the base field...
+    ('year', 1, 'short', 'příští rok'),
+    ('year', -1, 'narrow', 'minulý rok'),
+    # ...whereas month-short/week-short do define their own names.
+    ('month', 1, 'short', 'příští měs.'),
+    ('week', 1, 'short', 'příští týd.'),
+])
+def test_get_relative_name_cs_length_fallback(field: str, offset: int, length: str, expected: str):
+    assert dates.get_relative_name(field, offset, length=length, locale='cs') == expected
+
+
+@pytest.mark.parametrize(('field', 'offset', 'expected'), [
+    ('day', -2, 'i förrgår'),
+    ('day', -1, 'i går'),
+    ('day', 0, 'i dag'),
+    ('day', 1, 'i morgon'),
+    ('day', 2, 'i övermorgon'),
+    ('week', 1, 'nästa vecka'),
+    ('month', 0, 'den här månaden'),
+    ('year', -1, 'förra året'),
+    ('year', 0, 'i år'),
+    ('second', 0, 'nu'),
+    ('quarter', 1, 'nästa kvartal'),
+    ('mon', 1, 'måndag nästa vecka'),
+    ('sun', -1, 'söndag förra veckan'),
+])
+def test_get_relative_name_sv(field: str, offset: int, expected: str):
+    assert dates.get_relative_name(field, offset, locale='sv') == expected
+
+
+@pytest.mark.parametrize(('field', 'offset', 'length', 'expected'), [
+    ('day', -1, 'narrow', 'igår'),
+    ('day', 0, 'narrow', 'idag'),
+    ('day', 1, 'narrow', 'imorgon'),
+])
+def test_get_relative_name_sv_lengths(field: str, offset: int, length: str, expected: str):
+    assert dates.get_relative_name(field, offset, length=length, locale='sv') == expected
+
+
+@pytest.mark.parametrize(('field', 'offset', 'fmt', 'expected'), [
+    # Finnish 'long' uses "klo" joiner.
+    ('day', 1, 'long', 'huomenna klo 15.30.00 UTC'),
+    ('day', -1, 'long', 'eilen klo 15.30.00 UTC'),
+    ('day', -2, 'long', 'toissa päivänä klo 15.30.00 UTC'),
+    ('week', 1, 'long', 'ensi viikolla klo 15.30.00 UTC'),
+    ('year', -1, 'long', 'viime vuonna klo 15.30.00 UTC'),
+    ('mon', 1, 'long', 'ensi maanantaina klo 15.30.00 UTC'),
+    # Finnish 'short' has no "klo" joiner -> comma pattern.
+    ('day', 1, 'short', 'huomenna, 15.30'),
+])
+def test_format_relative_datetime_fi(field: str, offset: int, fmt: str, expected: str):
+    assert dates.format_relative_datetime(
+        dates.get_relative_name(field, offset, locale='fi'),
+        time(15, 30),
+        format=fmt,
+        locale='fi',
+    ) == expected
+
+
+@pytest.mark.parametrize(('field', 'offset', 'fmt', 'expected'), [
+    # Swedish 'long' uses "kl." joiner.
+    ('day', 1, 'long', 'i morgon kl. 15:30:00 UTC'),
+    ('day', -1, 'long', 'i går kl. 15:30:00 UTC'),
+    ('day', -2, 'long', 'i förrgår kl. 15:30:00 UTC'),
+    ('week', 1, 'long', 'nästa vecka kl. 15:30:00 UTC'),
+    ('year', -1, 'long', 'förra året kl. 15:30:00 UTC'),
+    ('mon', 1, 'long', 'måndag nästa vecka kl. 15:30:00 UTC'),
+    # Swedish 'medium' also uses "kl." joiner.
+    ('day', 1, 'medium', 'i morgon kl. 15:30:00'),
+    # Swedish 'short' has no relative pattern -> falls back to datetime_formats.
+    ('day', 1, 'short', 'i morgon 15:30'),
+])
+def test_format_relative_datetime_sv(field: str, offset: int, fmt: str, expected: str):
+    name = dates.get_relative_name(field, offset, locale='sv')
+    assert dates.format_relative_datetime(
+        name,
+        time(15, 30),
+        format=fmt,
+        locale='sv',
+    ) == expected
+
+
+def test_format_relative_datetime():
+    # English 'long': distinct "at" joiner
+    assert dates.format_relative_datetime(
+        'tomorrow', time(15, 30), format='long', locale='en',
+    ) == 'tomorrow at 3:30:00\u202fPM UTC'
+    # German 'long': "um" joiner
+    assert dates.format_relative_datetime(
+        'morgen', time(15, 30), format='long', locale='de',
+    ) == 'morgen um 15:30:00 UTC'
+    # French 'full': "à" joiner
+    assert dates.format_relative_datetime(
+        'demain', time(15, 30), format='full', locale='fr',
+    ) == 'demain à 15:30:00 temps universel coordonné'
+    # As of CLDR 48.2, Czech defines no `relative` patterns, so CLDR's root alias
+    # resolves them to the standard ones (ideally this would be "zítra v 15:30").
+    assert dates.format_relative_datetime(
+        'zítra', time(15, 30), format='short', locale='cs',
+    ) == 'zítra 15:30'
+    # Medium English has no distinctive relative pattern, so same as standard
+    assert dates.format_relative_datetime(
+        'tomorrow', time(15, 30), format='medium', locale='en',
+    ) == 'tomorrow, 3:30:00\u202fPM'
+
+
 def test_format_time(timezone_getter):
     t = time(15, 30)
     assert dates.format_time(t, locale='en_US') == '3:30:00\u202fPM'