diff --git a/holidays/groups/custom.py b/holidays/groups/custom.py
index dd54b26d5..2120aa1f1 100644
--- a/holidays/groups/custom.py
+++ b/holidays/groups/custom.py
@@ -10,6 +10,10 @@
 #  Website: https://github.com/vacanza/holidays
 #  License: MIT (see LICENSE file)
 
+from datetime import date
+
+from holidays.helpers import _normalize_tuple
+
 
 class StaticHolidays:
     """Helper class for special and substituted holidays support.
@@ -33,3 +37,11 @@ def __init__(self, cls) -> None:
             ):
                 setattr(self, attribute_name, value)
                 self.has_substituted_holidays = True
+
+        # Populate substituted holidays from adjacent years.
+        self.weekend_workdays = set()
+        for special_public_holidays in getattr(self, "special_public_holidays", {}).values():
+            for special_public_holiday in _normalize_tuple(special_public_holidays):
+                if len(special_public_holiday) == 5:  # The fifth element is the year.
+                    _, _, from_month, from_day, from_year = special_public_holiday
+                    self.weekend_workdays.add(date(from_year, from_month, from_day))
diff --git a/holidays/holiday_base.py b/holidays/holiday_base.py
index 052a4d137..2db65448c 100644
--- a/holidays/holiday_base.py
+++ b/holidays/holiday_base.py
@@ -233,7 +233,7 @@ def _populate(self, year):
     ones."""
     weekend: set[int] = {SAT, SUN}
     """Country weekend days."""
-    weekend_workdays: set[date] = set()
+    weekend_workdays: set[date]
     """Working days moved to weekends."""
     default_category: str = PUBLIC
     """The entity category used by default."""
@@ -362,7 +362,7 @@ def __init__(
         self.language = language.lower() if language else None
         self.observed = observed
         self.subdiv = subdiv
-        self.weekend_workdays = set()
+        self.weekend_workdays = getattr(self, "weekend_workdays", set())
 
         supported_languages = set(self.supported_languages)
         self.tr = (
diff --git a/tests/countries/test_azerbaijan.py b/tests/countries/test_azerbaijan.py
index 462b1359e..69da67629 100644
--- a/tests/countries/test_azerbaijan.py
+++ b/tests/countries/test_azerbaijan.py
@@ -66,6 +66,26 @@ def test_substituted_holidays(self):
             "2025-01-03",
         )
 
+        for year, dts in {
+            2012: (
+                "2012-12-29",
+                "2012-12-30",
+            ),
+            2013: (
+                "2013-12-28",
+                "2013-12-29",
+            ),
+            2019: (
+                "2019-12-28",
+                "2019-12-29",
+            ),
+            2023: ("2023-12-30",),
+            2024: ("2024-12-29",),
+        }.items():
+            az_holidays = Azerbaijan(years=year)
+            for dt in dts:
+                self.assertTrue(az_holidays.is_working_day(dt))
+
     def test_new_years_day(self):
         name = "Yeni il bayramı"
         self.assertHolidayName(name, (f"{year}-01-01" for year in range(1990, 2050)))
diff --git a/tests/countries/test_belarus.py b/tests/countries/test_belarus.py
index 3fe4dfe82..efabbcc8d 100644
--- a/tests/countries/test_belarus.py
+++ b/tests/countries/test_belarus.py
@@ -225,6 +225,18 @@ def test_radunitsa(self):
             "2030-05-07",
         )
 
+        for year, dts in {
+            2006: (
+                "2006-01-21",
+                "2006-05-06",
+                "2006-11-04",
+                "2006-12-30",
+            ),
+        }.items():
+            be_holidays = Belarus(years=year)
+            for dt in dts:
+                self.assertTrue(be_holidays.is_working_day(dt))
+
     def test_dzyady(self):
         name = "Дзень памяці"
 
diff --git a/tests/countries/test_china.py b/tests/countries/test_china.py
index 35f2ee4ef..d24ba1472 100644
--- a/tests/countries/test_china.py
+++ b/tests/countries/test_china.py
@@ -29,6 +29,50 @@ def test_no_holidays(self):
         self.assertNoHolidays(China(years=1949))
         self.assertNoHolidays(China(years=1949, categories=HALF_DAY))
 
+    def test_substituted_holidays(self):
+        for year, dts in {
+            2001: (
+                "2001-01-20",
+                "2001-01-21",
+                "2001-04-28",
+                "2001-04-29",
+                "2001-09-29",
+                "2001-09-30",
+                "2001-12-29",
+                "2001-12-30",
+            ),
+            2005: (
+                "2005-02-05",
+                "2005-02-06",
+                "2005-04-30",
+                "2005-05-08",
+                "2005-10-08",
+                "2005-10-09",
+                "2005-12-31",
+            ),
+            2006: (
+                "2006-01-28",
+                "2006-02-05",
+                "2006-04-29",
+                "2006-04-30",
+                "2006-09-30",
+                "2006-10-08",
+                "2006-12-30",
+                "2006-12-31",
+            ),
+            2011: (
+                "2011-01-30",
+                "2011-02-12",
+                "2011-04-02",
+                "2011-10-08",
+                "2011-10-09",
+                "2011-12-31",
+            ),
+        }.items():
+            cn_holidays = China(years=year)
+            for dt in dts:
+                self.assertTrue(cn_holidays.is_working_day(dt))
+
     def test_new_years_day(self):
         self.assertHolidayName("元旦", (f"{year}-01-01" for year in range(1950, 2050)))
 
diff --git a/tests/countries/test_kazakhstan.py b/tests/countries/test_kazakhstan.py
index 1567cc1a6..4b54ab1ba 100644
--- a/tests/countries/test_kazakhstan.py
+++ b/tests/countries/test_kazakhstan.py
@@ -242,6 +242,17 @@ def test_substituted_holidays(self):
             "2025-01-03",
         )
 
+        for year, dts in {
+            2013: (
+                "2013-05-04",
+                "2013-10-12",
+                "2013-12-28",
+            ),
+        }.items():
+            kz_holidays = Kazakhstan(years=year)
+            for dt in dts:
+                self.assertTrue(kz_holidays.is_working_day(dt))
+
     def test2022(self):
         self.assertHolidays(
             Kazakhstan(years=2022),
diff --git a/tests/countries/test_taiwan.py b/tests/countries/test_taiwan.py
index 515741d0d..72ba77097 100644
--- a/tests/countries/test_taiwan.py
+++ b/tests/countries/test_taiwan.py
@@ -28,6 +28,14 @@ def test_country_aliases(self):
     def test_no_holidays(self):
         self.assertNoHolidays(Taiwan(years=1911))
 
+    def test_substituted_holidays(self):
+        for year, dts in {
+            2014: ("2014-12-27",),
+        }.items():
+            tw_holidays = Taiwan(years=year)
+            for dt in dts:
+                self.assertTrue(tw_holidays.is_working_day(dt))
+
     def test_new_years_day(self):
         name = "中華民國開國紀念日"
         self.assertHolidayName(name, (f"{year}-01-01" for year in range(1990, 2030)))
diff --git a/tests/countries/test_ukraine.py b/tests/countries/test_ukraine.py
index 630b31bd3..2d64387c4 100644
--- a/tests/countries/test_ukraine.py
+++ b/tests/countries/test_ukraine.py
@@ -33,6 +33,18 @@ def test_no_holidays(self):
     def test_special_holidays(self):
         self.assertHoliday("1995-01-09")
 
+    def test_substituted_holidays(self):
+        for year, dts in {
+            1996: (
+                "1996-05-05",
+                "1996-05-12",
+                "1996-12-28",
+            ),
+        }.items():
+            ua_holidays = Ukraine(years=year)
+            for dt in dts:
+                self.assertTrue(ua_holidays.is_working_day(dt))
+
     def test_new_year_day(self):
         self.assertHoliday(f"{year}-01-01" for year in range(1991, 2023))
         dt = (
diff --git a/tests/countries/test_vietnam.py b/tests/countries/test_vietnam.py
index 38e74235a..00c420fce 100644
--- a/tests/countries/test_vietnam.py
+++ b/tests/countries/test_vietnam.py
@@ -174,6 +174,18 @@ def test_substituted_holidays(self):
             "2024-04-29",
         )
 
+        for year, dts in {
+            2014: (
+                "2014-04-26",
+                "2014-09-06",
+                "2014-12-27",
+            ),
+            2019: ("2019-01-05",),
+        }.items():
+            vn_holidays = Vietnam(years=year)
+            for dt in dts:
+                self.assertTrue(vn_holidays.is_working_day(dt))
+
     def test_l10n_default(self):
         self.assertLocalizedHolidays(
             ("2022-01-01", "Tết Dương lịch"),