Add country Singapore (SG)

Add country Singapore with its holidays as laid out in the [1998 Holidays Act](https://sso.agc.gov.sg/Act/HA1998).
This takes over the work done by @nathanielmiller23 from #108 and adapts it to the recent changes.

Signed-off-by: Thomas Lauf <thomas.lauf@tngtech.com>

Author: nathanielmiller23

ChangeLog

@@ -1,3 +1,5 @@
+- #143 SG: Add country Singapore (locale 'en-SG')
+       (thanks to nathanielmiller23)
 - #141 AU: Fix dates for 'Australia Day' and 'Anzac Day'
 
 2025.12.0

src/holidata/holidays/SG/__init__.py

@@ -0,0 +1,338 @@
+from dateutil.easter import EASTER_WESTERN
+
+from holidata.holiday import Country
+from holidata.utils import day, date, first
+
+__all__ = [
+    "SG",
+]
+
+"""
+Legal sources:
+- Holidays Act 1998 https://sso.agc.gov.sg/Act/HA1998
+- Parliamentary Elections Act 1954 https://sso.agc.gov.sg/Act/PEA1954
+- Presidential Elections Act 1991 https://sso.agc.gov.sg/Act/PrEA1991
+
+- https://www.mom.gov.sg/employment-practices/public-holidays
+- https://www.mom.gov.sg/employment-practices/public-holidays-entitlement-and-pay
+"""
+
+
+class SG(Country):
+    id = "SG"
+    languages = ["en"]
+    default_lang = "en"
+    regions = []
+    easter_type = EASTER_WESTERN
+
+    def __init__(self):
+        super().__init__()
+
+        self.define_holiday() \
+            .with_name("New Year's Day") \
+            .on(date(month=1, day=1)) \
+            .with_flags("NF") \
+
+        self.define_holiday() \
+            .with_name("New Year's Day (in lieu)") \
+            .on(first("monday").after(date(month=1, day=1))) \
+            .with_flags("NF") \
+            .on_condition(date(month=1, day=1).is_a("sunday"))
+
+        self.define_holiday() \
+            .with_name("Chinese New Year") \
+            .on(SG.chinese_new_year) \
+            .with_flags("NRV")
+
+        self.define_holiday() \
+            .with_name("Chinese New Year (Second Day)") \
+            .on(SG.chinese_new_year_day2) \
+            .with_flags("NRV")
+
+        self.define_holiday() \
+            .with_name("Chinese New Year (in lieu)") \
+            .on(SG.chinese_new_year_in_lieu) \
+            .with_flags("NRV")
+
+        self.define_holiday() \
+            .with_name("Good Friday") \
+            .on(day(2).before(self.easter())) \
+            .with_flags("NRV")
+
+        self.define_holiday() \
+            .with_name("Labour Day") \
+            .on(date(month=5, day=1)) \
+            .with_flags("NF") \
+
+        self.define_holiday() \
+            .with_name("Labour Day (in lieu)") \
+            .on(first("monday").after(date(month=5, day=1))) \
+            .with_flags("NF") \
+            .on_condition(date(month=5, day=1).is_a("sunday"))
+
+        self.define_holiday() \
+            .with_name("Hari Raya Puasa") \
+            .on(SG.hari_raya_puasa) \
+            .with_flags("NRV")
+
+        self.define_holiday() \
+            .with_name("Hari Raya Puasa (in lieu)") \
+            .on(SG.hari_raya_puasa_in_lieu) \
+            .with_flags("NRV")
+
+        self.define_holiday() \
+            .with_name("Vesak Day") \
+            .on(SG.vesak_day) \
+            .with_flags("NRV")
+
+        self.define_holiday() \
+            .with_name("Vesak Day (in lieu)") \
+            .on(SG.vesak_day_in_lieu) \
+            .with_flags("NRV")
+
+        self.define_holiday() \
+            .with_name("Hari Raya Haji") \
+            .on(SG.hari_raya_haji) \
+            .with_flags("NRV")
+
+        self.define_holiday() \
+            .with_name("Hari Raya Haji (in lieu)") \
+            .on(SG.hari_raya_haji_in_lieu) \
+            .with_flags("NRV")
+
+        self.define_holiday() \
+            .with_name("National Day") \
+            .on(date(month=8, day=9)) \
+            .with_flags("NF") \
+
+        self.define_holiday() \
+            .with_name("National Day (in lieu)") \
+            .on(first("monday").after(date(month=8, day=9))) \
+            .with_flags("NF") \
+            .on_condition(date(month=8, day=9).is_a("sunday"))
+
+        self.define_holiday() \
+            .with_name("Deepavali") \
+            .on(SG.deepavali) \
+            .with_flags("NRV")
+
+        self.define_holiday() \
+            .with_name("Deepavali (in lieu)") \
+            .on(SG.deepavali_in_lieu) \
+            .with_flags("NRV")
+
+        self.define_holiday() \
+            .with_name("Christmas Day") \
+            .on(date(month=12, day=25)) \
+            .with_flags("NRF") \
+
+        self.define_holiday() \
+            .with_name("Christmas Day (in lieu)") \
+            .on(first("monday").after(date(month=12, day=25))) \
+            .with_flags("NRF") \
+            .on_condition(date(month=12, day=25).is_a("sunday"))
+
+        """
+        General Election day
+        Holiday according to Section 35 of the Parliamentary Elections Act
+        """
+        self.define_holiday() \
+            .with_name("General Election") \
+            .on(SG.date_of_general_election) \
+            .with_flags("NF")
+
+        """
+        Presidential Election day
+        Holiday according to Section 17 of the Presidential Elections Act
+        """
+        self.define_holiday() \
+            .with_name("Presidential Election") \
+            .on(SG.date_of_presidential_election) \
+            .with_flags("NF")
+
+        """
+        SG50 Public holiday
+        Celebrating 50 years of independence from Malaysia
+        """
+        self.define_holiday() \
+            .with_name("SG50 Public Holiday") \
+            .on(date(month=8, day=7)) \
+            .in_years([2015]) \
+            .with_flags("NF")
+
+    @staticmethod
+    def date_of_general_election(year):
+        dates = {
+            2011: date(month=5, day=7),
+            2015: date(month=9, day=11),
+            2020: date(month=7, day=10),
+            2025: date(month=5, day=3),
+        }
+        return dates.get(year)(year) if year in dates else None
+
+    @staticmethod
+    def date_of_presidential_election(year):
+        dates = {
+            2011: date(month=8, day=27),
+            2017: date(month=9, day=13),
+            2023: date(month=9, day=1),
+        }
+        return dates.get(year)(year) if year in dates else None
+
+    @staticmethod
+    def chinese_new_year(year):
+        """Return the date of Chinese New Year for the given year."""
+        dates = {
+            2011: date(2, 3),
+            2012: date(1, 23),
+            2013: date(2, 10),
+            2014: date(1, 31),
+            2015: date(2, 19),
+            2016: date(2, 8),
+            2017: date(1, 28),
+            2018: date(2, 16),
+            2019: date(2, 5),
+            2020: date(1, 25),
+            2021: date(2, 12),
+            2022: date(2, 1),
+            2023: date(1, 22),
+            2024: date(2, 10),
+            2025: date(1, 29),
+            2026: date(2, 17)
+        }
+        return dates.get(year)(year) if year in dates else None
+
+    @staticmethod
+    def chinese_new_year_day2(year):
+        """Return the date of the second day of Chinese New Year."""
+        first_day = SG.chinese_new_year(year)
+        return first_day.shift(days=1) if first_day is not None else None
+
+    @staticmethod
+    def chinese_new_year_in_lieu(year):
+        holiday_date = SG.chinese_new_year(year)
+        if holiday_date is not None and holiday_date.weekday() == "saturday":
+            return holiday_date.shift_to_weekday("monday")
+        elif holiday_date is not None and holiday_date.weekday() == "sunday":
+            return holiday_date.shift_to_weekday("tuesday")
+        return None
+
+    @staticmethod
+    def hari_raya_puasa(year):
+        """Return the date of Hari Raya Puasa for the given year."""
+        dates = {
+            2011: date(8, 30),
+            2012: date(8, 19),
+            2013: date(8, 8),
+            2014: date(7, 28),
+            2015: date(7, 17),
+            2016: date(7, 6),
+            2017: date(6, 25),
+            2018: date(6, 15),
+            2019: date(6, 5),
+            2020: date(5, 24),
+            2021: date(5, 13),
+            2022: date(5, 3),
+            2023: date(4, 22),
+            2024: date(4, 10),
+            2025: date(3, 31),
+            2026: date(3, 21)
+        }
+        return dates.get(year)(year) if year in dates else None
+
+    @staticmethod
+    def hari_raya_puasa_in_lieu(year):
+        holiday_date = SG.hari_raya_puasa(year)
+        if holiday_date is not None and holiday_date.weekday() == "sunday":
+            return holiday_date.shift_to_weekday("monday")
+        return None
+
+    @staticmethod
+    def vesak_day(year):
+        """Return the date of Vesak Day for the given year."""
+        dates = {
+            2011: date(5, 17),
+            2012: date(5, 5),
+            2013: date(5, 24),
+            2014: date(5, 13),
+            2015: date(6, 1),
+            2016: date(5, 21),
+            2017: date(5, 10),
+            2018: date(5, 29),
+            2019: date(5, 19),
+            2020: date(5, 7),
+            2021: date(5, 26),
+            2022: date(5, 15),
+            2023: date(6, 2),
+            2024: date(5, 22),
+            2025: date(5, 12),
+            2026: date(5, 31)
+        }
+        return dates.get(year)(year) if year in dates else None
+
+    @staticmethod
+    def vesak_day_in_lieu(year):
+        holiday_date = SG.vesak_day(year)
+        if holiday_date is not None and holiday_date.weekday() == "sunday":
+            return holiday_date.shift_to_weekday("monday")
+        return None
+
+    @staticmethod
+    def hari_raya_haji(year):
+        """Return the date of Hari Raya Haji for the given year."""
+        dates = {
+            2011: date(11, 6),
+            2012: date(10, 26),
+            2013: date(10, 15),
+            2014: date(10, 5),
+            2015: date(9, 24),
+            2016: date(9, 12),
+            2017: date(9, 1),
+            2018: date(8, 22),
+            2019: date(8, 11),
+            2020: date(7, 31),
+            2021: date(7, 20),
+            2022: date(7, 10),
+            2023: date(6, 29),
+            2024: date(6, 17),
+            2025: date(6, 7),
+            2026: date(5, 27)
+        }
+        return dates.get(year)(year) if year in dates else None
+
+    @staticmethod
+    def hari_raya_haji_in_lieu(year):
+        holiday_date = SG.hari_raya_haji(year)
+        if holiday_date is not None and holiday_date.weekday() == "sunday":
+            return holiday_date.shift_to_weekday("monday")
+        return None
+
+    @staticmethod
+    def deepavali(year):
+        """Return the date of Deepavali for the given year."""
+        dates = {
+            2011: date(10, 26),
+            2012: date(11, 13),
+            2013: date(11, 2),
+            2014: date(10, 22),
+            2015: date(11, 10),
+            2016: date(10, 29),
+            2017: date(10, 18),
+            2018: date(11, 6),
+            2019: date(10, 27),
+            2020: date(11, 14),
+            2021: date(11, 4),
+            2022: date(10, 24),
+            2023: date(11, 12),
+            2024: date(10, 31),
+            2025: date(10, 20),
+            2026: date(11, 8)
+        }
+        return dates.get(year)(year) if year in dates else None
+
+    @staticmethod
+    def deepavali_in_lieu(year):
+        holiday_date = SG.deepavali(year)
+        if holiday_date is not None and holiday_date.weekday() == "sunday":
+            return holiday_date.shift_to_weekday("monday")
+        return None

src/holidata/holidays/__init__.py

@@ -25,6 +25,7 @@
 from .PT import *
 from .RU import *
 from .SE import *
+from .SG import *
 from .SI import *
 from .SK import *
 from .TR import *