From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Martijn Muijsers <martijnmuijsers@live.nl>
Date: Wed, 23 Nov 2022 16:29:01 +0100
Subject: [PATCH] Predict Halloween

License: GPL-3.0 (https://www.gnu.org/licenses/gpl-3.0.html)
Gale - https://galemc.org

The Halloween begins at 10/20 0:00 a.m., and end with 11/04 0:00 a.m.
Cache the date result to prevent calculate in every call

The JMH benchmark of this patch can be found in SunBox's `PredictHalloween`

diff --git a/net/minecraft/world/entity/ambient/Bat.java b/net/minecraft/world/entity/ambient/Bat.java
index 912b099a51269f92f250c7d6094ad41817749f93..a6487b63a277f7ca9681924850718f1dced746b1 100644
--- a/net/minecraft/world/entity/ambient/Bat.java
+++ b/net/minecraft/world/entity/ambient/Bat.java
@@ -245,11 +245,62 @@ public class Bat extends AmbientCreature {
         }
     }
 
+    // Gale start - predict Halloween
+    /**
+     * The 1-indexed month of the year that Halloween starts (inclusive).
+     */
+    private static final int halloweenStartMonthOfYear = 10;
+
+    /**
+     * The 1-indexed day of the month that Halloween starts (inclusive).
+     */
+    private static final int halloweenStartDayOfMonth = 20;
+
+    /**
+     * The 1-indexed month of the year that Halloween ends (exclusive).
+     */
+    private static final int halloweenEndMonthOfYear = 11;
+
+    /**
+     * The 1-indexed day of the month that Halloween ends (exclusive).
+     */
+    private static final int halloweenEndDayOfMonth = 4;
+
+    /**
+     * The next start of Halloween, given as milliseconds since the Unix epoch.
+     * Will be 0 while not computed yet.
+     */
+    private static long nextHalloweenStart = 0;
+
+    /**
+     * The next end of Halloween, given as milliseconds since the Unix epoch.
+     * Will be 0 while not computed yet.
+     */
+    private static long nextHalloweenEnd = 0;
+
     private static boolean isHalloween() {
-        LocalDate localDate = LocalDate.now();
-        int i = localDate.get(ChronoField.DAY_OF_MONTH);
-        int i1 = localDate.get(ChronoField.MONTH_OF_YEAR);
-        return i1 == 10 && i >= 20 || i1 == 11 && i <= 3;
+        long currentEpochMillis = System.currentTimeMillis();
+
+        // Update predicate
+        if (nextHalloweenEnd == 0 || currentEpochMillis >= nextHalloweenEnd) {
+            java.time.OffsetDateTime currentDate = java.time.OffsetDateTime.ofInstant(java.time.Instant.ofEpochMilli(currentEpochMillis), java.time.ZoneId.systemDefault())
+                .withHour(0).withMinute(0).withSecond(0).withNano(0); // Adjust to directly start or end at zero o'clock
+
+            java.time.OffsetDateTime thisHalloweenStart = currentDate.withMonth(halloweenStartMonthOfYear).withDayOfMonth(halloweenStartDayOfMonth);
+            java.time.OffsetDateTime thisHalloweenEnd = currentDate.withMonth(halloweenEndMonthOfYear).withDayOfMonth(halloweenEndDayOfMonth);
+
+            // Move to next year date if current passed
+            if (currentDate.isAfter(thisHalloweenEnd)) {
+                thisHalloweenStart = thisHalloweenStart.plusYears(1);
+                thisHalloweenEnd = thisHalloweenEnd.plusYears(1);
+            }
+
+            nextHalloweenStart = thisHalloweenStart.toInstant().toEpochMilli();
+            nextHalloweenEnd = thisHalloweenEnd.toInstant().toEpochMilli();
+        }
+
+        return currentEpochMillis >= nextHalloweenStart && currentEpochMillis < nextHalloweenEnd;
+        // Gale end - predict Halloween
     }
 
     private void setupAnimationStates() {