packages/SystemUI/res-keyguard/layout/default_clock_preview.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    >
    <TextClock
        android:id="@+id/time"
        style="@style/widget_big"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_above="@id/date"
        android:letterSpacing="0.03"
        android:gravity="center_horizontal"
        android:format12Hour="@string/keyguard_widget_12_hours_format"
        android:format24Hour="@string/keyguard_widget_24_hours_format"
        />

    <TextClock
        android:id="@+id/date"
        style="@stype/widget_big"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:letterSpacing="0.03"
        android:gravity="center_horizontal"
        android:format12Hour="EEE, MMM d"
        android:format24Hour="EEE, MMM d"
        />
</RelativeLayout>