/frameworks/base/core/res/res/values/config.xml
<!-- Control the default night mode to use when there is no other mode override set.
One of the following values (see UiModeManager.java):
0 - MODE_NIGHT_AUTO
1 - MODE_NIGHT_NO
2 - MODE_NIGHT_YES
tyd,lxd,def open night mode + UiModeManagerService.java
-->
<integer name="config_defaultNightMode">2</integer>
</resources>