diff --git a/hutool-core/src/test/java/cn/hutool/core/date/DateUtilTest.java b/hutool-core/src/test/java/cn/hutool/core/date/DateUtilTest.java
index 1f75a082c..974182dc4 100755
--- a/hutool-core/src/test/java/cn/hutool/core/date/DateUtilTest.java
+++ b/hutool-core/src/test/java/cn/hutool/core/date/DateUtilTest.java
@@ -954,6 +954,15 @@ public class DateUtilTest {
 		}
 	}
 
+	@Test
+	public void issueI9CYHITest() {
+		final long betweenDay = DateUtil.betweenDay(
+			DateUtil.parse("2024-03-01"),
+			DateUtil.parse("2024-03-31"), true);
+
+		Assert.assertEquals(30, betweenDay);
+	}
+
 	@Test
 	public void dayOfYearTest() {
 		final int dayOfYear = DateUtil.dayOfYear(DateUtil.parse("2020-01-01"));