[Android Themes] Ticklefish:
Not having the Touchwiz KK lockscreen, I'm going to have to do a bit of guessing here. Let's see how right I am..

This is your sec_single_clock.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:gravity="center_horizontal" android:orientation="vertical" android:id="@id/keyguard_single_clock" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_marginLeft="@dimen/kg_singleclock_margin_left" android:layout_marginTop="@dimen/kg_singleclock_margin_top"
xmlns:android="http://schemas.android.com/apk/res/android">
<LinearLayout android:gravity="bottom" android:layout_gravity="center_horizontal" android:orientation="horizontal" android:layout_width="wrap_content" android:layout_height="@dimen/kg_singleclock_height">
<com.android.keyguard.sec.SecKeyguardTextClock android:textSize="@dimen/kg_singleclock_time_text_size_normal" android:textColor="#ffffffff" android:gravity="bottom" android:id="@id/keyguard_single_clock_time" android:layout_width="wrap_content" android:layout_height="wrap_content" android:shadowColor="#cc000000" android:format12Hour="@string/status_view_12_hours_format" android:format24Hour="@string/status_view_24_hours_format" style="@style/keyguard_text_shadow" />
<com.android.keyguard.sec.SecKeyguardTextClock android:textSize="20.0dip" android:textColor="#ffffffff" android:id="@id/keyguard_single_clock_ampm" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginLeft="5.0dip" android:shadowColor="#cc000000" android:textAllCaps="true" android:format12Hour="@string/status_view_ampm_for_12_hours" android:format24Hour="@string/status_view_ampm_for_24_hours" style="@style/keyguard_text_shadow" />
</LinearLayout>
<LinearLayout android:layout_gravity="center_horizontal" android:orientation="horizontal" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginTop="8.0dip" android:layout_marginBottom="5.0dip">
<TextView android:textSize="@dimen/kg_widget_common_date_text_size" android:textColor="#ffffffff" android:id="@id/keyguard_single_clock_date" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginRight="20.0dip" android:shadowColor="#cc000000" style="@style/keyguard_text_shadow" />
<include layout="@layout/sec_alarm" />
</LinearLayout>
<include layout="@layout/sec_owner_info" />
</LinearLayout>

The thing that strikes me is that this xml has a width of fill_parent but the two LinearLayouts that contain the clock and the date have widths of wrap_content, which would make them aligned with the left side of the screen.

The first thing I'd try is changing those widths to fill_parent:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:gravity="center_horizontal" android:orientation="vertical" android:id="@id/keyguard_single_clock" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_marginLeft="@dimen/kg_singleclock_margin_left" android:layout_marginTop="@dimen/kg_singleclock_margin_top"
xmlns:android="http://schemas.android.com/apk/res/android">
<LinearLayout android:gravity="bottom" android:layout_gravity="center_horizontal" android:orientation="horizontal" android:layout_width="[COLOR="Red"]fill_parent[/COLOR]" android:layout_height="@dimen/kg_singleclock_height">
<com.android.keyguard.sec.SecKeyguardTextClock android:textSize="@dimen/kg_singleclock_time_text_size_normal" android:textColor="#ffffffff" android:gravity="bottom" android:id="@id/keyguard_single_clock_time" android:layout_width="wrap_content" android:layout_height="wrap_content" android:shadowColor="#cc000000" android:format12Hour="@string/status_view_12_hours_format" android:format24Hour="@string/status_view_24_hours_format" style="@style/keyguard_text_shadow" />
<com.android.keyguard.sec.SecKeyguardTextClock android:textSize="20.0dip" android:textColor="#ffffffff" android:id="@id/keyguard_single_clock_ampm" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginLeft="5.0dip" android:shadowColor="#cc000000" android:textAllCaps="true" android:format12Hour="@string/status_view_ampm_for_12_hours" android:format24Hour="@string/status_view_ampm_for_24_hours" style="@style/keyguard_text_shadow" />
</LinearLayout>
<LinearLayout android:layout_gravity="center_horizontal" android:orientation="horizontal" android:layout_width="[COLOR="Red"]fill_parent[/COLOR]" android:layout_height="wrap_content" android:layout_marginTop="8.0dip" android:layout_marginBottom="5.0dip">
<TextView android:textSize="@dimen/kg_widget_common_date_text_size" android:textColor="#ffffffff" android:id="@id/keyguard_single_clock_date" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginRight="20.0dip" android:shadowColor="#cc000000" style="@style/keyguard_text_shadow" />
<include layout="@layout/sec_alarm" />
</LinearLayout>
<include layout="@layout/sec_owner_info" />
</LinearLayout>

Give this code a try and see what happens.