feat: add Polish and pluralization support

- Update EnglishLocale schema to support dictionary-based pluralization for months and years using 'str | dict[str, str]'.
- Implement a centralized plural rule registry in plural_rules.py following Unicode CLDR standards.
- Refactor compute_time_span_string in date.py to select unit labels based on language-specific numeric rules.
- Add the Polish locale with grammatically correct paucal (few) and genitive plural (many) forms.

src/rendercv/renderer/templater/date.py

@@ -6,6 +6,7 @@ from rendercv.schema.models.cv.entries.bases.entry_with_complex_fields import (
 )
 from rendercv.schema.models.locale.locale import Locale
 
+from .plural_rules import get_plural_rules
 from .string_processor import substitute_placeholders
 
 
@@ -228,6 +229,50 @@ def compute_time_span_string(
     Returns:
         Formatted time span string with years and months.
     """
+
+    def _get_localized_label(
+        count: int,
+        singular_label: str,
+        plural_data: str | dict[str, str],
+        lang_iso: str,
+    ) -> str:
+        """Select the correct localized label based on count and language plural rules.
+
+        Why:
+            This helper function returns the appropriate singular, plural, or language-specific
+            plural form of a label based on the count value and the target language's pluralization rules.
+
+        Args:
+            count: The quantity used to determine which plural form to use.
+            singular_label: The label to return when count equals 1.
+            plural_data: Either a string (for simple plural forms) or a dictionary mapping
+                plural categories ('one', 'few', 'many', etc.) to their localized labels.
+            lang_iso: ISO 639-1 language code (e.g., 'en', 'de', 'ru') used to determine
+                plural rules and categories.
+
+        Returns:
+            The appropriate localized label (string) for the given count and language.
+            Returns an empty string if count is 0.
+            Returns singular_label if count is 1.
+            Returns the language-specific plural form from plural_data if count > 1.
+        """
+        if count == 0:
+            return ""
+
+        if count == 1:
+            return singular_label
+
+        if isinstance(plural_data, dict):
+            # Determine the category tag (one, few, many)
+            category = get_plural_rules(count, lang_iso)
+            # Return the specific form, or 'many' as a fallback
+            return plural_data.get(category, plural_data.get("many", ""))
+
+        # Fallback for standard string-based locales (english, german, etc.)
+        return plural_data
+
+    lang_iso = locale.language_iso_639_1
+
     if isinstance(start_date, int) or isinstance(end_date, int):
         # Then it means one of the dates is year, so time span cannot be more
         # specific than years.
@@ -236,15 +281,12 @@ def compute_time_span_string(
 
         time_span_in_years = end_year - start_year
 
-        if time_span_in_years < 2:
-            how_many_years = "1"
-            locale_years = locale.year
-        else:
-            how_many_years = str(time_span_in_years)
-            locale_years = locale.years
+        locale_years = _get_localized_label(
+            time_span_in_years, locale.year, locale.years, lang_iso
+        )
 
         placeholders: dict[str, str] = {
-            "HOW_MANY_YEARS": how_many_years,
+            "HOW_MANY_YEARS": str(time_span_in_years),
             "YEARS": locale_years,
             "HOW_MANY_MONTHS": "",
             "MONTHS": "",
@@ -268,31 +310,23 @@ def compute_time_span_string(
     how_many_months %= 12
 
     # Format the number of years and months between start_date and end_date:
-    if how_many_years == 0:
+    locale_years = _get_localized_label(
+        how_many_years, locale.year, locale.years, lang_iso
+    )
+    if locale_years == "":
         how_many_years = ""
-        locale_years = ""
-    elif how_many_years == 1:
-        how_many_years = "1"
-        locale_years = locale.year
-    else:
-        how_many_years = str(how_many_years)
-        locale_years = locale.years
 
     # Format the number of months between start_date and end_date:
-    if how_many_months == 0:
+    locale_months = _get_localized_label(
+        how_many_months, locale.month, locale.months, lang_iso
+    )
+    if locale_months == "":
         how_many_months = ""
-        locale_months = ""
-    elif how_many_months == 1:
-        how_many_months = "1"
-        locale_months = locale.month
-    else:
-        how_many_months = str(how_many_months)
-        locale_months = locale.months
 
     placeholders = {
-        "HOW_MANY_YEARS": how_many_years,
+        "HOW_MANY_YEARS": str(how_many_years),
         "YEARS": locale_years,
-        "HOW_MANY_MONTHS": how_many_months,
+        "HOW_MANY_MONTHS": str(how_many_months),
         "MONTHS": locale_months,
     }
     return substitute_placeholders(time_span_template, placeholders)

src/rendercv/renderer/templater/plural_rules.py

@@ -0,0 +1,57 @@
+# https://www.unicode.org/cldr/charts/48/supplemental/language_plural_rules.html
+
+
+def polish_rule(count: int) -> str:
+    if count == 1:
+        return "one"
+    if 2 <= count % 10 <= 4 and not (12 <= count % 100 <= 14):
+        return "few"
+    return "many"
+
+
+# Registry mapping ISO codes to rule functions
+PLURAL_RULES = {
+    "pl": polish_rule,
+    # add here new set of rules
+}
+
+
+def default_rule(n: int) -> str:
+    """Fallback rule for simple singular/plural languages."""
+    return "one" if n == 1 else "other"
+
+
+def get_plural_rules(count: int, language_code: str):
+    """Determine the appropriate CLDR (Unicode Common Locale Data Repository) plural category
+    for a given count and language code.
+
+    Why:
+        This function returns the grammatical plural category that should be used for a specific number in a given language. Different languages have different plural rules - for example, English has two forms (singular/plural), while Polish has three, and Arabic has six.
+
+    Example:
+        ```py
+        >>> get_plural_rules(1, "en")
+        'one'
+        >>> get_plural_rules(5, "en")
+        'other'
+        ```
+
+    Args:
+        count (int): The number for which to determine the plural category.
+        language_code (str): The ISO language code (e.g., 'en', 'pl', 'ar') identifying
+            which language's plural rules to apply.
+
+    Returns:
+        str: The CLDR plural category, typically one of: 'zero', 'one', 'two', 'few', 'many', or 'other'.
+            The exact categories available depend on the language's plural rules.
+
+    Note:
+        - This function relies on a PLURAL_RULES dictionary that maps language codes to their
+          respective plural rule functions.
+        - If the language_code is not found in PLURAL_RULES, a default_rule function is used
+          as a fallback.
+        - CLDR plural categories are used for proper localization and internationalization (i18n) of text that contains numbers.
+
+    """
+    rule = PLURAL_RULES.get(language_code, default_rule)
+    return rule(count)

src/rendercv/schema/models/locale/english_locale.py

@@ -33,7 +33,7 @@ class EnglishLocale(BaseModelWithoutExtraKeys):
         default="month",
         description='Translation of "month" (singular). The default value is `month`.',
     )
-    months: str = pydantic.Field(
+    months: str | dict[str, str] = pydantic.Field(
         default="months",
         description='Translation of "months" (plural). The default value is `months`.',
     )
@@ -41,7 +41,7 @@ class EnglishLocale(BaseModelWithoutExtraKeys):
         default="year",
         description='Translation of "year" (singular). The default value is `year`.',
     )
-    years: str = pydantic.Field(
+    years: str | dict[str, str] = pydantic.Field(
         default="years",
         description='Translation of "years" (plural). The default value is `years`.',
     )
@@ -131,6 +131,7 @@ class EnglishLocale(BaseModelWithoutExtraKeys):
             "arabic": "ar",
             "hebrew": "he",
             "persian": "fa",
+            "polish": "pl",
         }[self.language]
 
     @functools.cached_property

src/rendercv/schema/models/locale/other_locales/polish.yaml

@@ -0,0 +1,41 @@
+# yaml-language-server: $schema=../../../../../../schema.json
+locale:
+  language: polish 
+  last_updated: "Ostatnia aktualizacja"
+  month: "miesiąc"
+  months: 
+    one: "miesiąc"
+    few: "miesiące"
+    many: "miesięcy"
+  year: "rok"
+  years:
+    one: "rok"
+    few: "lata"
+    many: "lat"
+  present: "obecnie"
+  month_abbreviations:
+    - Sty 
+    - Lut 
+    - Mar
+    - Kwi 
+    - Maj
+    - Cze 
+    - Lip
+    - Sie 
+    - Wrz 
+    - Paź 
+    - Lis 
+    - Gru 
+  month_names:
+    - Styczeń 
+    - Luty 
+    - Marzec
+    - Kwiecień
+    - Maj
+    - Czerwiec
+    - Lipiec
+    - Sierpień
+    - Wrzesień
+    - Październik
+    - Listopad
+    - Grudzień