fix: Incorrect date-time reporting in the UI due to time zone handling (

#9)

This commit fixes the handling of UTC to local time zone conversion,
which was causing incorrect date-time display in the UI.

src/main/java/com/salesforce/datacloud/jdbc/core/accessor/impl/TimeStampVectorAccessor.java

@@ -24,9 +24,11 @@
 import java.sql.SQLException;
 import java.sql.Time;
 import java.sql.Timestamp;
+import java.time.Instant;
 import java.time.LocalDateTime;
+import java.time.ZoneOffset;
+import java.time.ZonedDateTime;
 import java.time.format.DateTimeFormatter;
-import java.time.temporal.ChronoUnit;
 import java.util.Calendar;
 import java.util.TimeZone;
 import java.util.concurrent.TimeUnit;
@@ -132,9 +134,10 @@ private LocalDateTime getLocalDateTime(Calendar calendar) {
 
         if (calendar != null) {
             TimeZone timeZone = calendar.getTimeZone();
-            long millis = this.timeUnit.toMillis(value);
-            localDateTime = localDateTime.minus(
-                    (long) timeZone.getOffset(millis) - (long) this.timeZone.getOffset(millis), ChronoUnit.MILLIS);
+            ZonedDateTime utcZonedDateTime =
+                    ZonedDateTime.ofInstant(Instant.ofEpochMilli(this.timeUnit.toMillis(value)), ZoneOffset.UTC);
+            localDateTime =
+                    utcZonedDateTime.withZoneSameInstant(timeZone.toZoneId()).toLocalDateTime();
         }
         return localDateTime;
     }

src/test/java/com/salesforce/datacloud/jdbc/core/accessor/impl/TimeStampVectorAccessorTest.java

@@ -21,7 +21,9 @@
 import com.salesforce.datacloud.jdbc.core.accessor.SoftAssertions;
 import com.salesforce.datacloud.jdbc.util.RootAllocatorTestExtension;
 import com.salesforce.datacloud.jdbc.util.TestWasNullConsumer;
+import java.sql.Timestamp;
 import java.time.Instant;
+import java.time.LocalDateTime;
 import java.time.format.DateTimeFormatterBuilder;
 import java.util.ArrayList;
 import java.util.Calendar;
@@ -486,6 +488,40 @@ void testNulledTimestampVector() {
         consumer.assertThat().hasNotNullSeen(0).hasNullSeen(NUM_OF_METHODS * values.size());
     }
 
+    @SneakyThrows
+    @Test
+    void testGetTimestampWithDifferentTimeZone() {
+        Calendar calendar = Calendar.getInstance();
+        calendar.setTimeZone(TimeZone.getTimeZone("UTC"));
+        List<Integer> monthNumber = getRandomMonthNumber();
+        val values = getMilliSecondValues(calendar, monthNumber);
+        val consumer = new TestWasNullConsumer(collector);
+
+        try (val vector = extension.createTimeStampNanoVector(values)) {
+            val i = new AtomicInteger(0);
+            val sut = new TimeStampVectorAccessor(vector, i::get, consumer);
+
+            Calendar pstCalendar = Calendar.getInstance(TimeZone.getTimeZone("PST"));
+
+            for (; i.get() < vector.getValueCount(); i.incrementAndGet()) {
+                val timestampValue = sut.getTimestamp(pstCalendar);
+                val stringValue = sut.getString();
+                val currentMillis = values.get(i.get());
+
+                pstCalendar.setTimeInMillis(currentMillis);
+                long pstMillis = pstCalendar.getTimeInMillis();
+
+                LocalDateTime expectedPST = LocalDateTime.ofInstant(
+                        Instant.ofEpochMilli(pstMillis),
+                        TimeZone.getTimeZone("PST").toZoneId());
+                Timestamp expectedTimestamp = Timestamp.valueOf(expectedPST);
+
+                collector.assertThat(timestampValue).isEqualTo(expectedTimestamp);
+                assertISOStringLike(stringValue, currentMillis);
+            }
+        }
+    }
+
     private List<Long> getMilliSecondValues(Calendar calendar, List<Integer> monthNumber) {
         List<Long> result = new ArrayList<>();
         for (int currentNumber : monthNumber) {