SUMMARY
The solar system viewer only uses 2 digits, which makes for going back to other years to compare things, a bit tricky. Though it can be done with large step sizes, the widget should allow and display at least 4 digit years. 

Only change that needs to be made is to kstars/kstars/tools/planetviewer.ui Which I'm trying to submit through Phabricator (For practice, though it's a really simple one, since everything already works, it's just display)

Change is this: 


diff --git a/kstars/tools/planetviewer.ui b/kstars/tools/planetviewer.ui
index e5aedeac8..b977a7997 100644
--- a/kstars/tools/planetviewer.ui
+++ b/kstars/tools/planetviewer.ui
@@ -79,7 +79,11 @@
       </spacer>
      </item>
      <item>
-      <widget class="QDateEdit" name="DateBox" />
+      <widget class="QDateEdit" name="DateBox">
+       <property name="displayFormat">
+        <string>M/d/yyyy</string>
+       </property>
+      </widget>
      </item>
      <item>
       <widget class="QPushButton" name="TodayButton" >