add testcase for issue #2426

core/src/main/java/com/alibaba/fastjson2/JSONFactory.java

@@ -522,4 +522,8 @@ public static ObjectWriterCreator getContextWriterCreator() {
     public interface JSONPathCompiler {
         JSONPath compile(Class objectClass, JSONPath path);
     }
+
+    public static String getDefaultWriterFormat() {
+        return defaultWriterFormat;
+    }
 }

core/src/test/java/com/alibaba/fastjson2/issues_2400/Issue2426.java

@@ -0,0 +1,27 @@
+package com.alibaba.fastjson2.issues_2400;
+
+import com.alibaba.fastjson2.JSON;
+import com.alibaba.fastjson2.JSONFactory;
+import com.alibaba.fastjson2.JSONWriter;
+import org.junit.jupiter.api.Test;
+
+import java.util.Date;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class Issue2426 {
+    @Test
+    public void test() {
+        String defaultWriterFormat = JSONFactory.getDefaultWriterFormat();
+        try {
+            JSON.configWriterDateFormat("yyyy-MM-dd'T'HH:mm:ss");
+            Date date = new Date(1712988987882L);
+            JSONWriter.Context writeContext = JSONFactory.createWriteContext();
+            String json = JSON.toJSONString(date, writeContext);
+            assertEquals("\"2024-04-13T14:16:27\"", json);
+        } finally {
+            JSON.configWriterDateFormat(defaultWriterFormat);
+        }
+        assertEquals(defaultWriterFormat, JSONFactory.getDefaultWriterFormat());
+    }
+}