Custom dark theme scheduling

allows the use to set the start and end automatic dark theme
activation within a day.

Test: run all settings tests
Change-Id: If96fc050159724d553acb09c2da4fab1d5ff519f

src/com/android/settings/display/darkmode/TimeFormatter.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the
+ * License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+package com.android.settings.display.darkmode;
+
+import android.content.Context;
+
+import java.time.LocalTime;
+import java.time.format.DateTimeFormatter;
+
+/**
+ * Formats LocalTime to the locale time string format
+*/
+public class TimeFormatter {
+    private final Context mContext;
+    public static DateTimeFormatter formatter = DateTimeFormatter.ofPattern("hh:mm a");
+    public TimeFormatter(Context context) {
+        mContext = context;
+    }
+
+    public String of(LocalTime time) {
+        return is24HourFormat() ? time.toString() : formatter.format(time);
+    }
+
+    public boolean is24HourFormat() {
+        return android.text.format.DateFormat.is24HourFormat(mContext);
+    }
+}