diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index 4bfcedd0..cf486a4f 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -8,3 +8,5 @@ parameters:
 
 	ignoreErrors:
 	    - '#Unsafe usage of new static#'
+	    - '#Cannot call method startOfDay\(\) on Carbon\\CarbonImmutable\|null#'
+	    - '#Cannot call method addDays\(\) on Carbon\\CarbonImmutable\|null#'
diff --git a/src/Calendars/IslamicCalendar.php b/src/Calendars/IslamicCalendar.php
index bb6b513b..9ab97a8c 100644
--- a/src/Calendars/IslamicCalendar.php
+++ b/src/Calendars/IslamicCalendar.php
@@ -72,7 +72,7 @@ protected function getHoliday(array $collection, int $year, int $totalDays): arr
 
     protected function createPeriod(string $date, int $year, int $totalDays): CarbonPeriod
     {
-        $start = CarbonImmutable::createFromFormat('Y-m-d', "{$year}-{$date}")->startOfDay();
+        $start = CarbonImmutable::createFromFormat('Y-m-d', "{$year}-{$date}")?->startOfDay();
         $end = $start->addDays($totalDays - 1)->startOfDay();
 
         return CarbonPeriod::create($start, '1 day', $end);
@@ -95,7 +95,7 @@ protected function getOverlapping(array $collection, int $year, int $totalDays):
             $date = end($date);
         }
 
-        $start = CarbonImmutable::createFromFormat('Y-m-d', "{$year}-{$date}")->startOfDay();
+        $start = CarbonImmutable::createFromFormat('Y-m-d', "{$year}-{$date}")?->startOfDay();
         $end = $start->addDays($totalDays - 1)->startOfDay();
 
         if ($end->year !== $year) {
diff --git a/src/Countries/Country.php b/src/Countries/Country.php
index 841c5c0d..a6ab1d72 100644
--- a/src/Countries/Country.php
+++ b/src/Countries/Country.php
@@ -5,6 +5,7 @@
 use Carbon\CarbonImmutable;
 use Carbon\CarbonInterface;
 use Carbon\CarbonPeriod;
+use Carbon\Exceptions\InvalidFormatException;
 use Spatie\Holidays\Contracts\HasTranslations;
 use Spatie\Holidays\Exceptions\InvalidCountry;
 use Spatie\Holidays\Exceptions\InvalidYear;
@@ -33,6 +34,10 @@ public function get(int $year, ?string $locale = null): array
                 }
             }
 
+            if ($date === null) {
+                throw new InvalidFormatException("Invalid date for holiday `{$name}`");
+            }
+
             if ($this instanceof HasTranslations) {
                 $name = $this->translate(basename(str_replace('\\', '/', static::class)), $name, $locale);
             }
diff --git a/src/Countries/Egypt.php b/src/Countries/Egypt.php
index d6f8af4e..37a6109e 100644
--- a/src/Countries/Egypt.php
+++ b/src/Countries/Egypt.php
@@ -4,6 +4,7 @@
 
 use Carbon\CarbonImmutable;
 use Carbon\CarbonInterface;
+use Carbon\Exceptions\InvalidFormatException;
 use Spatie\Holidays\Concerns\Translatable;
 use Spatie\Holidays\Contracts\HasTranslations;
 use Spatie\Holidays\Exceptions\InvalidYear;
@@ -304,6 +305,11 @@ private function getIslamicHolidayDatesForYear(array $holidayDates, int $year, s
 
         $startDay = CarbonImmutable::createFromFormat('Y-m-d', sprintf('%s-%s', $year, $holidayDates[$year]));
 
+        if ($startDay === null) {
+            throw new InvalidFormatException("Invalid date format for holiday: {$holidayName}");
+
+        }
+
         if ($duration === 1) {
             // For single-day holidays, use the holiday name without "Day"
             $dates[$holidayName] = $startDay;
diff --git a/src/Countries/Greece.php b/src/Countries/Greece.php
index 09540598..290a34f1 100644
--- a/src/Countries/Greece.php
+++ b/src/Countries/Greece.php
@@ -35,7 +35,7 @@ protected function variableHolidays(int $year): array
         $megaloSavvato = $orthodoxEaster->copy()->subDay();
         $deuteraPasha = $orthodoxEaster->copy()->addDay();
 
-        $protomagia = CarbonImmutable::createFromFormat('Y-m-d', "{$year}-05-01");
+        $protomagia = CarbonImmutable::createFromDate($year, 5, 1);
         $moveProtomagia = [$megaliParaskevi, $megaloSavvato, $orthodoxEaster, $deuteraPasha];
 
         if (in_array($protomagia, $moveProtomagia, true)) {
diff --git a/src/Countries/Netherlands.php b/src/Countries/Netherlands.php
index 34f3b37f..0e9fecb5 100644
--- a/src/Countries/Netherlands.php
+++ b/src/Countries/Netherlands.php
@@ -24,7 +24,7 @@ protected function allHolidays(int $year): array
     /** @return array<string, CarbonImmutable> */
     protected function variableHolidays(int $year): array
     {
-        $koningsDag = CarbonImmutable::createFromFormat('Y-m-d', "{$year}-04-27");
+        $koningsDag = CarbonImmutable::createFromDate($year, 4, 27);
 
         if ($koningsDag->isSunday()) {
             $koningsDag = $koningsDag->subDay();
diff --git a/src/Countries/Panama.php b/src/Countries/Panama.php
index 98e10eb1..c8229257 100644
--- a/src/Countries/Panama.php
+++ b/src/Countries/Panama.php
@@ -3,6 +3,7 @@
 namespace Spatie\Holidays\Countries;
 
 use Carbon\CarbonImmutable;
+use Carbon\Exceptions\InvalidFormatException;
 
 class Panama extends Country
 {
@@ -80,11 +81,14 @@ protected function calculateBridgeDays(array $fixedHolidays, int $year): array
         foreach ($fixedHolidays as $name => $date) {
             $holiday = CarbonImmutable::createFromFormat('Y-m-d', "{$year}-{$date}");
 
-            if ($holiday !== false) {
-                $holidays[$name] = $holiday;
-                if ($holiday->isSunday()) {
-                    $holidays[$name.' (Puente)'] = $holiday->addDay();
-                }
+            if ($holiday === null) {
+                throw new InvalidFormatException("Invalid date format for holiday: {$name}");
+            }
+
+            $holidays[$name] = $holiday;
+
+            if ($holiday->isSunday()) {
+                $holidays[$name.' (Puente)'] = $holiday->addDay();
             }
         }