add some Calendar open intent handling

app/src/main/AndroidManifest.xml

@@ -38,6 +38,15 @@
                 <data android:mimeType="text/x-vcalendar"/>
                 <data android:mimeType="text/calendar"/>
             </intent-filter>
+
+            <intent-filter>
+                <action android:name="android.intent.action.VIEW"/>
+                <category android:name="android.intent.category.DEFAULT"/>
+
+                <data android:mimeType="time/epoch"/>
+                <data android:host="com.android.calendar"/>
+                <data android:scheme="content"/>
+            </intent-filter>
         </activity>
 
         <activity

app/src/main/kotlin/com/simplemobiletools/calendar/activities/MainActivity.kt

@@ -81,12 +81,26 @@ class MainActivity : SimpleActivity(), NavigationListener {
         calendar_fab.setOnClickListener { launchNewEventIntent() }
         checkWhatsNewDialog()
         storeStoragePaths()
+
         if (resources.getBoolean(R.bool.portrait_only))
             requestedOrientation = ActivityInfo.SCREEN_ORIENTATION_PORTRAIT
 
         if (intent?.action == Intent.ACTION_VIEW && intent.data != null) {
-            tryImportEventsFromFile(intent.data)
+            val uri = intent.data
+            if (uri.authority == "com.android.calendar") {
+                // clicking date on a widget: content://com.android.calendar/time/1507309245683
+                if (intent?.extras?.getBoolean("DETAIL_VIEW", false) == true) {
+                    val timestamp = uri.pathSegments.last()
+                    if (timestamp.areDigitsOnly()) {
+                        openDayAt(timestamp.toLong())
+                        return
+                    }
+                }
+            } else {
+                tryImportEventsFromFile(uri)
+            }
         }
+
         storeStateVariables()
         updateViewPager()
 
@@ -578,6 +592,14 @@ class MainActivity : SimpleActivity(), NavigationListener {
         mIsMonthSelected = true
     }
 
+    private fun openDayAt(timestamp: Long) {
+        val dayCode = Formatter.getDayCodeFromTS((timestamp / 1000).toInt())
+        Intent(this, DayActivity::class.java).apply {
+            putExtra(DAY_CODE, dayCode)
+            startActivity(this)
+        }
+    }
+
     override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<String>, grantResults: IntArray) {
         super.onRequestPermissionsResult(requestCode, permissions, grantResults)