顶级目录：/frameworks/base/packages/SettingsProvider/

修改文件：res/values/defaults.xml

+ <string name="def_sprd_default_time_12_24" translatable="false">24</string>

修改文件：src/com/android/providers/settings/DatabaseHelper.java

private void loadSystemSettings(SQLiteDatabase db) {
         * See: SettingsProvider.UpgradeController#onUpgradeLocked
         */
+		loadStringSetting(stmt, Settings.System.TIME_12_24, R.string.def_sprd_default_time_12_24);
    } finally {
        if (stmt != null) stmt.close();
    }
}