From 88c959c4ed42b75f03add908e35a561fabb1e9bf Mon Sep 17 00:00:00 2001
From: Looly <loolly@gmail.com>
Date: Thu, 23 Mar 2023 22:34:21 +0800
Subject: [PATCH] =?UTF-8?q?=E4=BF=AE=E5=A4=8DCalendarUtil.isSameMonth?=
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---
 CHANGELOG.md                                  |  3 ++-
 .../cn/hutool/core/date/CalendarUtil.java     |  7 ++++--
 .../cn/hutool/core/date/Issue3011Test.java    | 23 +++++++++++++++++++
 3 files changed, 30 insertions(+), 3 deletions(-)
 create mode 100644 hutool-core/src/test/java/cn/hutool/core/date/Issue3011Test.java

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4ae3607fa..1ac5ef3f3 100755
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,7 +2,7 @@
 # 🚀Changelog
 
 -------------------------------------------------------------------------------------------------------------
-# 5.8.16.M1 (2023-03-20)
+# 5.8.16.M1 (2023-03-23)
 
 ### 🐣新特性
 * 【core  】      改进Calculator.conversion，兼容乘法符号省略写法（issue#2964@Github）
@@ -17,6 +17,7 @@
 * 【core  】      修复FileMagicNumber长度判断问题导致的越界异常（issue#I6MACI@Gitee）
 * 【core  】      修复DateUtil针对ISO8601时间格式部分场景下的解析存在问题（issue#2981@Github）
 * 【core  】      修复JSONUtil.toBean可能的空指针问题（issue#2987@Github）
+* 【core  】      修复CalendarUtil.isSameMonth没有判断公元前导致不一致的问题（issue#3011@Github）
 
 -------------------------------------------------------------------------------------------------------------
 # 5.8.15 (2023-03-09)
diff --git a/hutool-core/src/main/java/cn/hutool/core/date/CalendarUtil.java b/hutool-core/src/main/java/cn/hutool/core/date/CalendarUtil.java
index 80ce668d4..4a0f6ae91 100644
--- a/hutool-core/src/main/java/cn/hutool/core/date/CalendarUtil.java
+++ b/hutool-core/src/main/java/cn/hutool/core/date/CalendarUtil.java
@@ -395,7 +395,8 @@ public class CalendarUtil {
 	}
 
 	/**
-	 * 比较两个日期是否为同一月
+	 * 比较两个日期是否为同一月<br>
+	 * 同一个月的意思是：ERA（公元）、year（年）、month（月）都一致。
 	 *
 	 * @param cal1 日期1
 	 * @param cal2 日期2
@@ -407,7 +408,9 @@ public class CalendarUtil {
 			throw new IllegalArgumentException("The date must not be null");
 		}
 		return cal1.get(Calendar.YEAR) == cal2.get(Calendar.YEAR) && //
-				cal1.get(Calendar.MONTH) == cal2.get(Calendar.MONTH);
+				cal1.get(Calendar.MONTH) == cal2.get(Calendar.MONTH) &&
+				// issue#3011@Github
+				cal1.get(Calendar.ERA) == cal2.get(Calendar.ERA);
 	}
 
 	/**
diff --git a/hutool-core/src/test/java/cn/hutool/core/date/Issue3011Test.java b/hutool-core/src/test/java/cn/hutool/core/date/Issue3011Test.java
new file mode 100644
index 000000000..d28f81f76
--- /dev/null
+++ b/hutool-core/src/test/java/cn/hutool/core/date/Issue3011Test.java
@@ -0,0 +1,23 @@
+package cn.hutool.core.date;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.Calendar;
+
+public class Issue3011Test {
+	@Test
+	public void isSameMonthTest() {
+		// https://github.com/dromara/hutool/issues/3011
+		// 判断是否同一个月，还需考虑公元前和公元后的的情况
+		// 此处公元前2020年和公元2021年返回年都是2021
+		final Calendar calendar1 = Calendar.getInstance();
+		calendar1.set(-2020, Calendar.FEBRUARY, 12);
+
+		final Calendar calendar2 = Calendar.getInstance();
+		calendar2.set(2021, Calendar.FEBRUARY, 12);
+
+
+		Assert.assertFalse(DateUtil.isSameMonth(calendar1, calendar2));
+	}
+}