[Google Pixel 2 XL Guides, News, & Discussion] Tulsadiver:
There has been some confusion about the ability to have a true center clock for Pie due to the notch made for Pixel 3 XL. This guide will show you how to center the clock and also move it to the right assuming you know how to decompile and recompile your SystemUIGoogle.apk. Find the statusbar.xml in the res/layout folder.

Center Clock

Find the code for the clock:

<com.android.systemui.statusbar.policy.Clock android:textAppearance="@style/TextAppearance.StatusBar.Clock" android:gravity="start|center" android:id="@id/clock" android:layout_width="wrap_content" android:layout_height="fill_parent" android:singleLine="true" android:paddingStart="@dimen/status_bar_left_clock_starting_padding" android:paddingEnd="@dimen/status_bar_left_clock_end_padding" />

Copy/Cut it and move it to just under this code which is located near the top:

xmlns:systemui="http://schemas.android.com/apk/res/com.android.systemui">

Remove the padding from the clock's code. Change the android:gravity from start|center to just center and change the android:layout_width from wrap_content to fill_parent. The resulting clock code will read like this:

<com.android.systemui.statusbar.policy.Clock android:textAppearance="@style/TextAppearance.StatusBar.Clock" android:gravity="center" android:id="@id/clock" android:layout_width="fill_parent" android:layout_height="fill_parent" android:singleLine="true" />

The entire statusbar.xml will now look like this:

<?xml version="1.0" encoding="utf-8"?>
<com.android.systemui.statusbar.phone.PhoneStatusBarView android:orientation="vertical" android:id="@id/status_bar" android:background="@drawable/system_bar_background" android:focusable="false" android:descendantFocusability="afterDescendants" android:layout_width="fill_parent" android:layout_height="@dimen/status_bar_height" android:accessibilityPaneTitle="@string/status_bar"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:systemui="http://schemas.android.com/apk/res/com.android.systemui">
<com.android.systemui.statusbar.policy.Clock android:textAppearance="@style/TextAppearance.StatusBar.Clock" android:gravity="center" android:id="@id/clock" android:layout_width="fill_parent" android:layout_height="fill_parent" android:singleLine="true" />
<ImageView android:id="@id/notification_lights_out" android:paddingBottom="2.0dip" android:visibility="gone" android:layout_width="@dimen/status_bar_icon_size" android:layout_height="fill_parent" android:src="@drawable/ic_sysbar_lights_out_dot_small" android:scaleType="center" android:paddingStart="@dimen/status_bar_padding_start" />
<LinearLayout android:orientation="horizontal" android:id="@id/status_bar_contents" android:layout_width="fill_parent" android:layout_height="fill_parent" android:paddingStart="@dimen/status_bar_padding_start" android:paddingEnd="@dimen/status_bar_padding_end">
<ViewStub android:id="@id/operator_name" android:layout="@layout/operator_name" android:layout_width="wrap_content" android:layout_height="fill_parent" />
<FrameLayout android:layout_width="0.0dip" android:layout_height="fill_parent" android:layout_weight="1.0">
<include layout="@layout/heads_up_status_bar_layout" />
<LinearLayout android:id="@id/status_bar_left_side" android:clipChildren="false" android:layout_width="fill_parent" android:layout_height="fill_parent"> <com.android.systemui.statusbar.AlphaOptimizedFrameLayout android:orientation="horizontal" android:id="@id/notification_icon_area" android:clipChildren="false" android:layout_width="0.0dip" android:layout_height="fill_parent" android:layout_weight="1.0" />
</LinearLayout>
</FrameLayout>
<android.widget.Space android:gravity="center" android:id="@id/cutout_space_view" android:layout_width="0.0dip" android:layout_height="fill_parent" /> <com.android.keyguard.AlphaOptimizedLinearLayout android:gravity="end|center" android:orientation="horizontal" android:id="@id/system_icon_area" android:layout_width="0.0dip" android:layout_height="fill_parent" android:layout_weight="1.0">
<include layout="@layout/system_icons" /> </com.android.keyguard.AlphaOptimizedLinearLayout>
</LinearLayout>
<ViewStub android:id="@id/emergency_cryptkeeper_text" android:layout="@layout/emergency_cryptkeeper_text" android:layout_width="wrap_content" android:layout_height="fill_parent" />
</com.android.systemui.statusbar.phone.PhoneStatusBarView>

Right Clock

Find the code:

<com.android.keyguard.AlphaOptimizedLinearLayout android:gravity="end|center" android:orientation="horizontal" android:id="@id/system_icon_area" android:layout_width="0.0dip" android:layout_height="fill_parent" android:layout_weight="1.0">

and change it to this:

<com.android.keyguard.AlphaOptimizedLinearLayout android:orientation="horizontal" android:id="@id/system_icon_area" android:layout_width="wrap_content" android:layout_height="fill_parent">

Just under that code will be this:

<include layout="@layout/system_icons" />

Immediately under that code add this:

<android.widget.Space android:gravity="center" android:id="@id/cutout_space_view" android:layout_width="0.0dip" android:layout_height="fill_parent" />

Now for the clock code. Like the center clock mode copy/cut the clock code and place it immediately under the above code you just added. Remove the existing padding and replace it with this:

android:paddingLeft="4.0dip"

so that the entire clock code reads like this:

<com.android.systemui.statusbar.policy.Clock android:textAppearance="@style/TextAppearance.StatusBar.Clock" android:gravity="start|center" android:id="@id/clock" android:layout_width="wrap_content" android:layout_height="fill_parent" android:paddingLeft="4.0dip" android:singleLine="true" />

And the finished statusbar.xml should read like this:

<?xml version="1.0" encoding="utf-8"?>
<com.android.systemui.statusbar.phone.PhoneStatusBarView android:orientation="vertical" android:id="@id/status_bar" android:background="@drawable/system_bar_background" android:focusable="false" android:descendantFocusability="afterDescendants" android:layout_width="fill_parent" android:layout_height="@dimen/status_bar_height" android:accessibilityPaneTitle="@string/status_bar"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:systemui="http://schemas.android.com/apk/res/com.android.systemui">
<ImageView android:id="@id/notification_lights_out" android:paddingBottom="2.0dip" android:visibility="gone" android:layout_width="@dimen/status_bar_icon_size" android:layout_height="fill_parent" android:src="@drawable/ic_sysbar_lights_out_dot_small" android:scaleType="center" android:paddingStart="@dimen/status_bar_padding_start" />
<LinearLayout android:orientation="horizontal" android:id="@id/status_bar_contents" android:layout_width="fill_parent" android:layout_height="fill_parent" android:paddingStart="@dimen/status_bar_padding_start" android:paddingEnd="@dimen/status_bar_padding_end">
<ViewStub android:id="@id/operator_name" android:layout="@layout/operator_name" android:layout_width="wrap_content" android:layout_height="fill_parent" />
<FrameLayout android:layout_width="0.0dip" android:layout_height="fill_parent" android:layout_weight="1.0">
<include layout="@layout/heads_up_status_bar_layout" />
<LinearLayout android:id="@id/status_bar_left_side" android:clipChildren="false" android:layout_width="fill_parent" android:layout_height="fill_parent">
<com.android.systemui.statusbar.AlphaOptimizedFrameLayout android:orientation="horizontal" android:id="@id/notification_icon_area" android:clipChildren="false" android:layout_width="0.0dip" android:layout_height="fill_parent" android:layout_weight="1.0" />
</LinearLayout>
</FrameLayout>
<android.widget.Space android:gravity="center" android:id="@id/cutout_space_view" android:layout_width="0.0dip" android:layout_height="fill_parent" />
<com.android.keyguard.AlphaOptimizedLinearLayout android:orientation="horizontal" android:id="@id/system_icon_area" android:layout_width="wrap_content" android:layout_height="fill_parent">
<include layout="@layout/system_icons" />
<android.widget.Space android:gravity="center" android:id="@id/cutout_space_view" android:layout_width="0.0dip" android:layout_height="fill_parent" />
<com.android.systemui.statusbar.policy.Clock android:textAppearance="@style/TextAppearance.StatusBar.Clock" android:gravity="start|center" android:id="@id/clock" android:layout_width="wrap_content" android:layout_height="fill_parent" android:paddingLeft="4.0dip" android:singleLine="true" /> </com.android.keyguard.AlphaOptimizedLinearLayout>
</LinearLayout>
<ViewStub android:id="@id/emergency_cryptkeeper_text" android:layout="@layout/emergency_cryptkeeper_text" android:layout_width="wrap_content" android:layout_height="fill_parent" />
</com.android.systemui.statusbar.phone.PhoneStatusBarView>