代码路径：
frameworks/base/packages/SettingsProvider/res/values/defaults.xml
frameworks/base/packages/SettingsProvider/src/com/android/providers/settings/DatabaseHelper.java
设置默认GPS校时

 <bool name="def_auto_time_gps">true</bool>

设置默认打开GPS，这里有网络和GPS两种方式，如果只需要GPS就把network去掉

 <string name="def_location_providers_allowed" translatable="false">network,gps</string>
  <bool name="assisted_gps_enabled">true</bool>

设置24小时制
在defaults.xml文件中将time_12_24变量设置为24

<string name="time_12_24">24</string>  

在DatabaseHelper.java文件中loadSystemSettings()方法中加载到数据库中

 private void loadSystemSettings(SQLiteDatabase db) {
        SQLiteStatement stmt = null;
        try {
            stmt = db.compileStatement("INSERT OR IGNORE INTO system(name,value)"
                    + " VALUES(?,?);");		
      loadStringSetting(stmt, Settings.System.TIME_12_24, R.string.time_12_24);
}