diff --git a/app/src/main/java/com/rtbishop/lookingsat/MainActivity.kt b/app/src/main/java/com/rtbishop/lookingsat/MainActivity.kt
index d7d3d263..c991742b 100644
--- a/app/src/main/java/com/rtbishop/lookingsat/MainActivity.kt
+++ b/app/src/main/java/com/rtbishop/lookingsat/MainActivity.kt
@@ -1,11 +1,15 @@
 package com.rtbishop.lookingsat
 
 import android.os.Bundle
+import android.os.CountDownTimer
 import android.view.Menu
 import android.view.MenuItem
+import android.view.View
+import android.widget.TextView
 import android.widget.Toast
 import androidx.appcompat.app.AppCompatActivity
 import androidx.appcompat.widget.Toolbar
+import androidx.constraintlayout.widget.ConstraintLayout
 import androidx.drawerlayout.widget.DrawerLayout
 import androidx.lifecycle.ViewModelProviders
 import androidx.navigation.findNavController
@@ -13,38 +17,76 @@ import androidx.navigation.ui.AppBarConfiguration
 import androidx.navigation.ui.navigateUp
 import androidx.navigation.ui.setupActionBarWithNavController
 import androidx.navigation.ui.setupWithNavController
-import com.google.android.material.floatingactionbutton.FloatingActionButton
 import com.google.android.material.navigation.NavigationView
-import com.google.android.material.snackbar.Snackbar
+import java.util.*
+import java.util.concurrent.TimeUnit
 
 class MainActivity : AppCompatActivity() {
 
     private lateinit var appBarConfig: AppBarConfiguration
     private lateinit var mainViewModel: MainViewModel
+    private lateinit var timerLayout: ConstraintLayout
+    private lateinit var timeToAos: TextView
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         setContentView(R.layout.activity_main)
+        setupViews()
+        setupNavigation()
+        setupTimer()
+    }
 
+    private fun setupViews() {
         mainViewModel = ViewModelProviders.of(this).get(MainViewModel::class.java)
+        timerLayout = findViewById(R.id.timer_layout)
+        timeToAos = findViewById(R.id.time_to_aos)
+    }
 
+    private fun setupNavigation() {
         val toolbar: Toolbar = findViewById(R.id.toolbar)
         setSupportActionBar(toolbar)
 
-        val fab: FloatingActionButton = findViewById(R.id.fab)
-        fab.setOnClickListener { view ->
-            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
-                .setAction("Action", null).show()
-        }
-
         val drawerLayout: DrawerLayout = findViewById(R.id.drawer_layout)
         val navView: NavigationView = findViewById(R.id.nav_view)
         val navController = findNavController(R.id.nav_host)
 
-        appBarConfig =
-            AppBarConfiguration(setOf(R.id.nav_sky, R.id.nav_radar, R.id.nav_map), drawerLayout)
+        appBarConfig = AppBarConfiguration(setOf(R.id.nav_sky), drawerLayout)
         setupActionBarWithNavController(navController, appBarConfig)
         navView.setupWithNavController(navController)
+
+        navController.addOnDestinationChangedListener { _, destination, _ ->
+            if (destination.id == R.id.nav_sky) {
+                timerLayout.visibility = View.VISIBLE
+            } else {
+                timerLayout.visibility = View.GONE
+            }
+        }
+    }
+
+    private fun setupTimer() {
+        val cal = Calendar.getInstance()
+        cal.add(Calendar.DAY_OF_MONTH, 1)
+        cal.set(Calendar.HOUR_OF_DAY, 0)
+        cal.set(Calendar.MINUTE, 0)
+        cal.set(Calendar.SECOND, 0)
+        cal.set(Calendar.MILLISECOND, 0)
+        val totalMillis = cal.timeInMillis - System.currentTimeMillis()
+
+        val timer = object : CountDownTimer(totalMillis, 1000) {
+            override fun onFinish() {
+                Toast.makeText(this@MainActivity, "Time is up!", Toast.LENGTH_SHORT).show()
+            }
+
+            override fun onTick(millisUntilFinished: Long) {
+                timeToAos.text = String.format(
+                    resources.getString(R.string.next_aos_pattern),
+                    TimeUnit.MILLISECONDS.toHours(millisUntilFinished) % 60,
+                    TimeUnit.MILLISECONDS.toMinutes(millisUntilFinished) % 60,
+                    TimeUnit.MILLISECONDS.toSeconds(millisUntilFinished) % 60
+                )
+            }
+        }
+        timer.start()
     }
 
     override fun onSupportNavigateUp(): Boolean {
diff --git a/app/src/main/res/layout/app_bar_main.xml b/app/src/main/res/layout/app_bar_main.xml
index 353840fb..d41e2801 100644
--- a/app/src/main/res/layout/app_bar_main.xml
+++ b/app/src/main/res/layout/app_bar_main.xml
@@ -16,7 +16,30 @@
             android:layout_width="match_parent"
             android:layout_height="?attr/actionBarSize"
             android:background="?attr/colorPrimary"
-            app:popupTheme="@style/AppTheme.PopupOverlay" />
+            app:popupTheme="@style/AppTheme.PopupOverlay">
+
+            <androidx.constraintlayout.widget.ConstraintLayout
+                android:id="@+id/timer_layout"
+                android:layout_width="match_parent"
+                android:layout_height="match_parent">
+
+                <TextView
+                    android:id="@+id/time_to_aos"
+                    android:layout_width="0dp"
+                    android:layout_height="wrap_content"
+                    android:layout_marginEnd="16dp"
+                    android:gravity="center"
+                    android:text="@string/next_aos_pattern"
+                    android:textSize="24sp"
+                    app:layout_constraintBottom_toBottomOf="parent"
+                    app:layout_constraintEnd_toEndOf="parent"
+                    app:layout_constraintHorizontal_bias="0.5"
+                    app:layout_constraintStart_toStartOf="parent"
+                    app:layout_constraintTop_toTopOf="parent" />
+
+            </androidx.constraintlayout.widget.ConstraintLayout>
+
+        </androidx.appcompat.widget.Toolbar>
 
     </com.google.android.material.appbar.AppBarLayout>
 
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index 89e2fd7a..8c94b1cf 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -22,5 +22,6 @@
     <string name="height_def">64</string>
     <string name="height_summary">Ground station height in meters AMSL</string>
 
+    <string name="next_aos_pattern">Next AOS in %02d:%02d:%02d</string>
     <string name="placeholder">Placeholder</string>
 </resources>