diff --git a/zkdoc/release-note b/zkdoc/release-note
index e4e6a0f8a1..804662d7ff 100644
--- a/zkdoc/release-note
+++ b/zkdoc/release-note
@@ -17,6 +17,7 @@ ZK 10.1.0
   ZK-5787: aria-hidden elements do not contain focusable elements
   ZK-5743: clicking menuitem fires 2 onClick events in mobile browser
   ZK-5594: ListboxDataLoader doGroupsDataChange finds incorrect offset, causes class cast exception
+  ZK-5475: select a date with time produces an invalid result under locale pt
 
 * Upgrade Notes
   + Remove Htmls.encodeJavaScript(), Strings.encodeJavaScript(), Strings.escape() with Strings.ESCAPE_JAVASCRIPT, and replace them with OWASP Java Encoder APIs instead.
diff --git a/zktest/src/main/webapp/test2/B101-ZK-5475.zul b/zktest/src/main/webapp/test2/B101-ZK-5475.zul
new file mode 100644
index 0000000000..887908c1e3
--- /dev/null
+++ b/zktest/src/main/webapp/test2/B101-ZK-5475.zul
@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<!--
+B101-ZK-5475.zul
+
+	Purpose:
+
+	Description:
+
+	History:
+		2024/9/18, Created by jumperchen
+
+Copyright (C) 2024 Potix Corporation. All Rights Reserved.
+
+-->
+<zk>
+	<label multiline="true">
+		1. The datebox should show the date "13 de junho de 2024 00:00:00".
+		2. Please change "00:00:00" to "00:00:01" and then blur the datebox.
+		3. If you see the date "13 de junho de 2024 00:00:01" in the datebox, the test is OK. Otherwise, any error happens it's a bug.
+	</label>
+	<datebox cols="30" format="d 'de' MMMM y HH:mm:ss" onCreate='self.valueInLocalDate = java.time.LocalDate.parse("2024-06-13")' locale="pt" />
+</zk>
+
diff --git a/zktest/src/main/webapp/test2/config.properties b/zktest/src/main/webapp/test2/config.properties
index 27b8a328c2..c242fd57c4 100644
--- a/zktest/src/main/webapp/test2/config.properties
+++ b/zktest/src/main/webapp/test2/config.properties
@@ -3136,6 +3136,7 @@ B90-ZK-4431.zul=A,E,Multislider
 ##zats##B101-ZK-5787.zul=A,E,WCAG,Accessibility,Focus,Tabindex,Aria-hidden
 ##zats##B101-ZK-5743.zul=A,E,Compressed,JS,Debug-JS,TabletUI,Mobile,onClick
 ##zats##B101-ZK-5594.zul=A,E,Group,ListGroup,ROD,zkmax,Exception
+##zats##B101-ZK-5475.zul=A,E,Datebox,PT,Locale,Format,Constraint
 
 ##
 # Features - 3.0.x version
diff --git a/zktest/src/test/java/org/zkoss/zktest/zats/test2/B101_ZK_5475Test.java b/zktest/src/test/java/org/zkoss/zktest/zats/test2/B101_ZK_5475Test.java
new file mode 100644
index 0000000000..cd919a72c9
--- /dev/null
+++ b/zktest/src/test/java/org/zkoss/zktest/zats/test2/B101_ZK_5475Test.java
@@ -0,0 +1,34 @@
+/* B101_ZK_5475Test.java
+
+	Purpose:
+
+	Description:
+
+	History:
+		2:48 PM 2024/9/18, Created by jumperchen
+
+Copyright (C) 2024 Potix Corporation. All Rights Reserved.
+*/
+package org.zkoss.zktest.zats.test2;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+import org.zkoss.test.webdriver.WebDriverTestCase;
+
+/**
+ * @author jumperchen
+ */
+public class B101_ZK_5475Test extends WebDriverTestCase {
+	@Test
+	public void test() {
+		connect();
+		assertEquals("13 de junho 2024 00:00:00", jq(".z-datebox-input").val());
+		type(jq(".z-datebox-input"), "13 de junho 2024 00:00:01");
+		blur(jq(".z-datebox-input"));
+		waitResponse(true);
+		assertEquals(0, jq(".z-errorbox").length());
+		assertEquals("13 de junho 2024 00:00:01", jq(".z-datebox-input").val());
+	}
+}
diff --git a/zul/src/main/resources/web/js/zul/db/datefmt.ts b/zul/src/main/resources/web/js/zul/db/datefmt.ts
index 100e7c19e8..b41f7ce66f 100644
--- a/zul/src/main/resources/web/js/zul/db/datefmt.ts
+++ b/zul/src/main/resources/web/js/zul/db/datefmt.ts
@@ -267,6 +267,8 @@ var DateFmt = {
 				era = eras[eraKey];
 		}
 
+		fmt = fmt.replace(/'.*?'/g, ' '); //ZK-5475 remove any string enclosed by single quotes
+
 		var refDate = refval._moment.toDate(),
 			localeDateTimeFormat = new Intl.DateTimeFormat(localizedSymbols.LAN_TAG, { year: 'numeric' }),
 			eraName = localizedSymbols.ERA || (eraKey ? eraKey : this.getEraName(refDate, localizedSymbols, localeDateTimeFormat)),