Fix useDaylightTime for zh_TW (and other locales).

TimeZone.useDaylightTime shouldn't report whether a locale has *ever* used DST,
but whether a locale uses DST "these days". Taiwan is an example supported
locale that historically used DST but hasn't used it since 1980.

Bug: 877

2 files changed, 27 insertions, 3 deletions

diff --git a/luni/src/main/java/org/apache/harmony/luni/internal/util/ZoneInfo.java b/luni/src/main/java/org/apache/harmony/luni/internal/util/ZoneInfo.java
index 110a0fd..01319e1 100644
--- a/luni/src/main/java/org/apache/harmony/luni/internal/util/ZoneInfo.java
+++ b/luni/src/main/java/org/apache/harmony/luni/internal/util/ZoneInfo.java
@@ -111,12 +111,23 @@ public class ZoneInfo extends TimeZone {
 
         // Subtract the raw offset from all offsets so it can be changed
         // and affect them too.
-        // Find whether there exist any observances of DST.
-
         for (int i = 0; i < mGmtOffs.length; i++) {
             mGmtOffs[i] -= mRawOffset;
+        }
 
-            if (mIsDsts[i] != 0) {
+        // Is this zone still observing DST?
+        // We don't care if they've historically used it: most places have at least once.
+        // We want to know whether the last "schedule info" (the unix times in the mTransitions
+        // array) is in the future. If it is, DST is still relevant.
+        // See http://code.google.com/p/android/issues/detail?id=877.
+        // This test means that for somewhere like Morocco, which tried DST in 2009 but has
+        // no future plans (and thus no future schedule info) will report "true" from
+        // useDaylightTime at the start of 2009 but "false" at the end. This seems appropriate.
+        long currentUnixTime = System.currentTimeMillis() / 1000;
+        if (mTransitions.length > 0) {
+            // (We're really dealing with uint32_t values, so long is most convenient in Java.)
+            long latestScheduleTime = mTransitions[mTransitions.length - 1] & 0xffffffff;
+            if (currentUnixTime < latestScheduleTime) {
                 mUseDst = true;
             }
         }
diff --git a/luni/src/test/java/tests/api/java/util/TimeZoneTest.java b/luni/src/test/java/tests/api/java/util/TimeZoneTest.java
index efdb8a1..75e9ae3 100644
--- a/luni/src/test/java/tests/api/java/util/TimeZoneTest.java
+++ b/luni/src/test/java/tests/api/java/util/TimeZoneTest.java
@@ -383,6 +383,19 @@ public class TimeZoneTest extends junit.framework.TestCase {
     @TestTargetNew(
         level = TestLevel.COMPLETE,
         notes = "",
+        method = "useDaylightTime",
+        args = {}
+    )
+    public void test_useDaylightTime() {
+        // http://code.google.com/p/android/issues/detail?id=877
+        
+        TimeZone asiaTaipei = TimeZone.getTimeZone("Asia/Taipei");
+        assertFalse("Taiwan doesn't use DST", asiaTaipei.useDaylightTime());
+    }
+    
+    @TestTargetNew(
+        level = TestLevel.COMPLETE,
+        notes = "",
         method = "setID",
         args = {java.lang.String.class}
     )