fix(platform): normalize legacy Vietnam timezone

src/main/java/com/lab/labtimesheet/LabtimesheetApplication.java

@@ -1,23 +1,43 @@
 package com.lab.labtimesheet;
 
+import java.util.TimeZone;
+
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 
 import com.lab.labtimesheet.config.SecurityProperties;
 
-/** Application entry point and root component-scan boundary for Lab Timesheet. */
+/**
+ * Application entry point and root component-scan boundary for Lab Timesheet.
+ *
+ * <p>The entry point also canonicalizes the legacy Windows Vietnam timezone alias before database
+ * drivers inspect the JVM default timezone.
+ */
 @SpringBootApplication
 @EnableConfigurationProperties(SecurityProperties.class)
 public class LabtimesheetApplication {
+    private static final String LEGACY_VIETNAM_TIME_ZONE = "Asia/Saigon";
+    private static final String BUSINESS_TIME_ZONE = "Asia/Ho_Chi_Minh";
 
     /**
-     * Starts the standalone Spring Boot process.
+     * Canonicalizes the process timezone and starts the standalone Spring Boot process.
      *
      * @param args command-line arguments forwarded to Spring Boot
      */
     public static void main(String[] args) {
+        normalizeDefaultTimeZone();
         SpringApplication.run(LabtimesheetApplication.class, args);
     }
 
+    /**
+     * Replaces the legacy Windows Vietnam alias before pgJDBC sends it to PostgreSQL as a startup
+     * parameter. Other supported system timezones remain unchanged.
+     */
+    static void normalizeDefaultTimeZone() {
+        if (LEGACY_VIETNAM_TIME_ZONE.equals(TimeZone.getDefault().getID())) {
+            TimeZone.setDefault(TimeZone.getTimeZone(BUSINESS_TIME_ZONE));
+        }
+    }
+
 }