[Galaxy 3 Themes and Apps] V!KR@M:
Since the clock(marked as red) is on its own individual line, we can move it wherever we want, in cm7.

status_bar.xml in cm7:

<LinearLayout android:orientation="horizontal" android:id="@id/icons" android:layout_width="fill_parent" android:layout_height="fill_parent">
<com.android.systemui.statusbar.IconMerger android:gravity="center_vertical" android:orientation="horizontal" android:id="@id/notificationIcons" android:paddingLeft="6.0dip" android:layout_width="0.0dip" android:layout_height="fill_parent" android:layout_weight="1.0" android:layout_alignParentLeft="true" />
<LinearLayout android:gravity="center_vertical" android:orientation="horizontal" android:id="@id/statusIcons" android:paddingRight="1.0dip" android:layout_width="wrap_content" android:layout_height="fill_parent" android:layout_alignParentRight="true" />
<com.android.systemui.statusbar.CmSignalText android:textAppearance="@android:style/TextAppearance.StatusBar.Icon" android:gravity="center_vertical" android:orientation="horizontal" android:paddingRight="2.0dip" android:layout_width="wrap_content" android:layout_height="fill_parent" />
<com.android.systemui.statusbar.CmBatteryText android:textAppearance="@android:style/TextAppearance.StatusBar.Icon" android:gravity="center_vertical" android:orientation="horizontal" android:paddingRight="2.0dip" android:layout_width="wrap_content" android:layout_height="fill_parent" />
<com.android.systemui.statusbar.CmBatteryMiniIcon android:textAppearance="@android:style/TextAppearance.StatusBar.Icon" android:gravity="center_vertical" android:orientation="horizontal" android:id="@id/CmBatteryMiniIcon" android:layout_width="wrap_content" android:layout_height="fill_parent" />
[COLOR="Red"]<com.android.systemui.statusbar.Clock android:textAppearance="@android:style/TextAppearance.StatusBar.Icon" android:gravity="left|center" android:paddingRight="6.0dip" android:layout_width="wrap_content" android:layout_height="fill_parent" android:singleLine="true" />[/COLOR]
<LinearLayout android:orientation="horizontal" android:id="@id/buttons" android:layout_width="wrap_content" android:layout_height="fill_parent">
<ImageButton android:id="@id/status_edge_left" android:background="@drawable/ic_statusbar_edge_right_bottom" android:layout_width="wrap_content" android:layout_height="wrap_content" />
<ImageButton android:id="@id/status_home" android:background="@drawable/ic_statusbar_home_bottom" android:layout_width="wrap_content" android:layout_height="wrap_content" />
<ImageButton android:id="@id/status_sep1" android:background="@drawable/ic_statusbar_sep_bottom" android:layout_width="wrap_content" android:layout_height="wrap_content" />
<ImageButton android:id="@id/status_menu" android:background="@drawable/ic_statusbar_menu_bottom" android:layout_width="wrap_content" android:layout_height="wrap_content" />
<ImageButton android:id="@id/status_sep2" android:background="@drawable/ic_statusbar_sep_bottom" android:layout_width="wrap_content" android:layout_height="wrap_content" />
<ImageButton android:id="@id/status_back" android:background="@drawable/ic_statusbar_back_bottom" android:layout_width="wrap_content" android:layout_height="wrap_content" />
<ImageButton android:id="@id/status_sep3" android:background="@drawable/ic_statusbar_sep_bottom" android:layout_width="wrap_content" android:layout_height="wrap_content" />
<ImageButton android:id="@id/status_search" android:background="@drawable/ic_statusbar_search_bottom" android:layout_width="wrap_content" android:layout_height="wrap_content" />
<ImageButton android:id="@id/status_sep4" android:background="@drawable/ic_statusbar_sep_bottom" android:layout_width="wrap_content" android:layout_height="wrap_content" />
<ImageButton android:id="@id/status_quick_na" android:background="@drawable/ic_statusbar_na_up_bottom" android:layout_width="wrap_content" android:layout_height="wrap_content" />
<ImageButton android:id="@id/status_sep5" android:background="@drawable/ic_statusbar_sep_bottom" android:visibility="gone" android:layout_width="wrap_content" android:layout_height="wrap_content" />
<ImageButton android:id="@id/status_hide" android:background="@drawable/ic_statusbar_hide_bottom" android:visibility="gone" android:layout_width="wrap_content" android:layout_height="wrap_content" />
<ImageButton android:id="@id/status_edge_right" android:background="@drawable/ic_statusbar_edge_left_bottom" android:visibility="gone" android:layout_width="wrap_content" android:layout_height="wrap_content" />
</LinearLayout>
</LinearLayout>

Whereas in froyo, there's no such line in xmls. Also looks like the clock is called by the same process as that of battery and signal. So unfortunately, centering clock is not possible on froyo