Use isShownInPickerAt instead of isShownInPicker.

The latter is being removed.
The date(1 Jan 2019 00:00) was a cut-off date used in
SettingsUI. This change moves it to reuse that date without
duplication.
Affected method is used in setup wizard to answer "What time zone
IDs should we show for a country?". The question is vague, but
the change keeps user experience consistent across device w/o
breaking method contract.

Bug: 155738410
Test: presubmit
Change-Id: Ib139b316e5909cab18d015b7c163bb9c79bcef5b

1 files changed, 31 insertions, 2 deletions

diff --git a/core/java/android/util/TimeUtils.java b/core/java/android/util/TimeUtils.java
index cd6585cd3fa1..5fd0c33ca205 100644
--- a/core/java/android/util/TimeUtils.java
+++ b/core/java/android/util/TimeUtils.java
@@ -30,6 +30,7 @@ import com.android.i18n.timezone.ZoneInfoDb;
 
 import java.io.PrintWriter;
 import java.text.SimpleDateFormat;
+import java.time.Instant;
 import java.time.LocalTime;
 import java.util.ArrayList;
 import java.util.Calendar;
@@ -43,11 +44,39 @@ import java.util.List;
 public class TimeUtils {
     /** @hide */ public TimeUtils() {}
     /** {@hide} */
-    private static SimpleDateFormat sLoggingFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
+    private static final SimpleDateFormat sLoggingFormat =
+            new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
 
     /** @hide */
     public static final SimpleDateFormat sDumpDateFormat =
             new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
+
+    /**
+     * This timestamp is used in TimeUtils methods and by the SettingsUI to filter time zones
+     * to only "effective" ones in a country. It is compared against the notUsedAfter metadata that
+     * Android records for some time zones.
+     *
+     * <p>What is notUsedAfter?</p>
+     * Android chooses to avoid making users choose between functionally identical time zones at the
+     * expense of not being able to represent local times in the past.
+     *
+     * notUsedAfter exists because some time zones can "merge" with other time zones after a given
+     * point in time (i.e. they change to have identical transitions, offsets, display names, etc.).
+     * From the notUsedAfter time, the zone will express the same local time as the one it merged
+     * with.
+     *
+     * <p>Why hardcoded?</p>
+     * Rather than using System.currentTimeMillis(), a timestamp known to be in the recent past is
+     * used to ensure consistent behavior across devices and time, and avoid assumptions that the
+     * system clock on a device is currently set correctly. The fixed value should be updated
+     * occasionally, but it doesn't have to be very often as effective time zones for a country
+     * don't change very often.
+     *
+     * @hide
+     */
+    public static final Instant MIN_USE_DATE_OF_TIMEZONE =
+            Instant.ofEpochMilli(1546300800000L); // 1/1/2019 00:00 UTC
+
     /**
      * Tries to return a time zone that would have had the specified offset
      * and DST value at the specified moment in the specified country.
@@ -109,7 +138,7 @@ public class TimeUtils {
 
         List<String> timeZoneIds = new ArrayList<>();
         for (TimeZoneMapping timeZoneMapping : countryTimeZones.getTimeZoneMappings()) {
-            if (timeZoneMapping.isShownInPicker()) {
+            if (timeZoneMapping.isShownInPickerAt(MIN_USE_DATE_OF_TIMEZONE)) {
                 timeZoneIds.add(timeZoneMapping.getTimeZoneId());
             }
         }