Rename DateTimeUtils' createCalendar() to createGregorianCalendar()

Renames DateTimeUtils' createCalendar() to createGregorianCalendar() and improves the javadoc.

h2/src/main/org/h2/expression/Function.java

@@ -1252,7 +1252,7 @@ public class Function extends Expression implements FunctionCall {
         case TRUNCATE: {
             if (v0.getType() == Value.TIMESTAMP) {
                 java.sql.Timestamp d = v0.getTimestamp();
-                Calendar c = DateTimeUtils.createCalendar();
+                Calendar c = DateTimeUtils.createGregorianCalendar();
                 c.setTime(d);
                 c.set(Calendar.HOUR_OF_DAY, 0);
                 c.set(Calendar.MINUTE, 0);
@@ -1261,7 +1261,7 @@ public class Function extends Expression implements FunctionCall {
                 result = ValueTimestamp.fromMillis(c.getTimeInMillis());
             } else if (v0.getType() == Value.DATE) {
                 ValueDate vd = (ValueDate) v0;
-                Calendar c = DateTimeUtils.createCalendar();
+                Calendar c = DateTimeUtils.createGregorianCalendar();
                 c.setTime(vd.getDate());
                 c.set(Calendar.HOUR_OF_DAY, 0);
                 c.set(Calendar.MINUTE, 0);
@@ -1270,7 +1270,7 @@ public class Function extends Expression implements FunctionCall {
                 result = ValueTimestamp.fromMillis(c.getTimeInMillis());
             } else if (v0.getType() == Value.STRING) {
                 ValueString vd = (ValueString) v0;
-                Calendar c = DateTimeUtils.createCalendar();
+                Calendar c = DateTimeUtils.createGregorianCalendar();
                 c.setTime(ValueTimestamp.parse(vd.getString(), session.getDatabase().getMode()).getDate());
                 c.set(Calendar.HOUR_OF_DAY, 0);
                 c.set(Calendar.MINUTE, 0);
@@ -1822,7 +1822,7 @@ public class Function extends Expression implements FunctionCall {
         if (count > Integer.MAX_VALUE) {
             throw DbException.getInvalidValueException("DATEADD count", count);
         }
-        Calendar calendar = DateTimeUtils.createCalendar();
+        Calendar calendar = DateTimeUtils.createGregorianCalendar();
         int nanos = d.getNanos() % 1000000;
         calendar.setTime(d);
         calendar.add(field, (int) count);
@@ -1846,7 +1846,7 @@ public class Function extends Expression implements FunctionCall {
      */
     private static long datediff(String part, Timestamp d1, Timestamp d2) {
         int field = getDatePart(part);
-        Calendar calendar = DateTimeUtils.createCalendar();
+        Calendar calendar = DateTimeUtils.createGregorianCalendar();
         long t1 = d1.getTime(), t2 = d2.getTime();
         // need to convert to UTC, otherwise we get inconsistent results with
         // certain time zones (those that are 30 minutes off)
@@ -1896,7 +1896,7 @@ public class Function extends Expression implements FunctionCall {
         default:
             break;
         }
-        calendar = DateTimeUtils.createCalendar(TimeZone.getTimeZone("UTC"));
+        calendar = DateTimeUtils.createGregorianCalendar(TimeZone.getTimeZone("UTC"));
         calendar.setTimeInMillis(t1);
         int year1 = calendar.get(Calendar.YEAR);
         int month1 = calendar.get(Calendar.MONTH);

h2/src/main/org/h2/jdbc/JdbcResultSet.java

@@ -3799,7 +3799,7 @@ public class JdbcResultSet extends TraceObject implements ResultSet, JdbcResultS
         } else if (type == java.util.Date.class) {
             return type.cast(new java.util.Date(value.getTimestamp().getTime()));
         } else if (type == Calendar.class) {
-            Calendar calendar = DateTimeUtils.createCalendar();
+            Calendar calendar = DateTimeUtils.createGregorianCalendar();
             calendar.setTime(value.getTimestamp());
             return type.cast(calendar);
         } else if (type == UUID.class) {

h2/src/main/org/h2/util/DateTimeUtils.java

@@ -73,7 +73,7 @@ public class DateTimeUtils {
      * use a fixed value throughout the duration of the JVM's life, rather than
      * have this offset change, possibly midway through a long-running query.
      */
-    private static int zoneOffsetMillis = DateTimeUtils.createCalendar()
+    private static int zoneOffsetMillis = DateTimeUtils.createGregorianCalendar()
             .get(Calendar.ZONE_OFFSET);
 
     private DateTimeUtils() {
@@ -86,7 +86,7 @@ public class DateTimeUtils {
      */
     public static void resetCalendar() {
         CACHED_CALENDAR.remove();
-        zoneOffsetMillis = DateTimeUtils.createCalendar().get(Calendar.ZONE_OFFSET);
+        zoneOffsetMillis = DateTimeUtils.createGregorianCalendar().get(Calendar.ZONE_OFFSET);
     }
 
     /**
@@ -97,7 +97,7 @@ public class DateTimeUtils {
     private static Calendar getCalendar() {
         Calendar c = CACHED_CALENDAR.get();
         if (c == null) {
-            c = DateTimeUtils.createCalendar();
+            c = DateTimeUtils.createGregorianCalendar();
             CACHED_CALENDAR.set(c);
         }
         c.clear();
@@ -113,7 +113,7 @@ public class DateTimeUtils {
     private static Calendar getCalendar(TimeZone tz) {
         Calendar c = CACHED_CALENDAR_NON_DEFAULT_TIMEZONE.get();
         if (c == null || !c.getTimeZone().equals(tz)) {
-            c = DateTimeUtils.createCalendar(tz);
+            c = DateTimeUtils.createGregorianCalendar(tz);
             CACHED_CALENDAR_NON_DEFAULT_TIMEZONE.set(c);
         }
         c.clear();
@@ -121,21 +121,29 @@ public class DateTimeUtils {
     }
 
     /**
-     * Creates a calendar for the default timezone.
+     * Creates a Gregorian calendar for the default timezone using the default
+     * locale. Dates in H2 are represented in a Gregorian calendar. So this
+     * method should be used instead of Calendar.getInstance() to ensure that
+     * the Gregorian calendar is used for all date processing instead of a
+     * default locale calendar that can be non-Gregorian in some locales.
      *
-     * @return a calendar instance. A cached instance is returned where possible
+     * @return a new calendar instance.
      */
-    public static Calendar createCalendar() {
+    public static Calendar createGregorianCalendar() {
         return new GregorianCalendar();
     }
 
     /**
-     * Creates a calendar for the given timezone.
+     * Creates a Gregorian calendar for the given timezone using the default
+     * locale. Dates in H2 are represented in a Gregorian calendar. So this
+     * method should be used instead of Calendar.getInstance() to ensure that
+     * the Gregorian calendar is used for all date processing instead of a
+     * default locale calendar that can be non-Gregorian in some locales.
      *
      * @param tz timezone for the calendar, is never null
-     * @return a calendar instance. A cached instance is returned where possible
+     * @return a new calendar instance.
      */
-    public static Calendar createCalendar(TimeZone tz) {
+    public static Calendar createGregorianCalendar(TimeZone tz) {
         return new GregorianCalendar(tz);
     }
 
@@ -272,7 +280,7 @@ public class DateTimeUtils {
             throw DbException.getInvalidValueException("calendar", null);
         }
         target = (Calendar) target.clone();
-        Calendar local = DateTimeUtils.createCalendar();
+        Calendar local = DateTimeUtils.createGregorianCalendar();
         local.setTime(x);
         convertTime(local, target);
         return target.getTime().getTime();
@@ -548,7 +556,7 @@ public class DateTimeUtils {
      * @return the day of the week, Monday as 1 to Sunday as 7
      */
     public static int getIsoDayOfWeek(java.util.Date date) {
-        Calendar cal = DateTimeUtils.createCalendar();
+        Calendar cal = DateTimeUtils.createGregorianCalendar();
         cal.setTimeInMillis(date.getTime());
         int val = cal.get(Calendar.DAY_OF_WEEK) - 1;
         return val == 0 ? 7 : val;
@@ -569,7 +577,7 @@ public class DateTimeUtils {
      * @return the week of the year
      */
     public static int getIsoWeek(java.util.Date date) {
-        Calendar c = DateTimeUtils.createCalendar();
+        Calendar c = DateTimeUtils.createGregorianCalendar();
         c.setTimeInMillis(date.getTime());
         c.setFirstDayOfWeek(Calendar.MONDAY);
         c.setMinimalDaysInFirstWeek(4);
@@ -584,7 +592,7 @@ public class DateTimeUtils {
      * @return the year
      */
     public static int getIsoYear(java.util.Date date) {
-        Calendar cal = DateTimeUtils.createCalendar();
+        Calendar cal = DateTimeUtils.createGregorianCalendar();
         cal.setTimeInMillis(date.getTime());
         cal.setFirstDayOfWeek(Calendar.MONDAY);
         cal.setMinimalDaysInFirstWeek(4);
@@ -959,7 +967,7 @@ public class DateTimeUtils {
      * @return the new timestamp
      */
     public static Timestamp addMonths(Timestamp refDate, int nrOfMonthsToAdd) {
-        Calendar calendar = DateTimeUtils.createCalendar();
+        Calendar calendar = DateTimeUtils.createGregorianCalendar();
         calendar.setTime(refDate);
         calendar.add(Calendar.MONTH, nrOfMonthsToAdd);
 

h2/src/main/org/h2/util/ToDateParser.java

@@ -21,7 +21,7 @@ public class ToDateParser {
     private final ConfigParam functionName;
     private String inputStr;
     private String formatStr;
-    private final Calendar resultCalendar = DateTimeUtils.createCalendar();
+    private final Calendar resultCalendar = DateTimeUtils.createGregorianCalendar();
     private Integer nanos;
 
     /**
@@ -33,7 +33,7 @@ public class ToDateParser {
     private ToDateParser(ConfigParam functionName, String input, String format) {
         // reset calendar - default oracle behaviour
         resultCalendar.set(Calendar.YEAR, 1970);
-        resultCalendar.set(Calendar.MONTH, DateTimeUtils.createCalendar().get(Calendar.MONTH));
+        resultCalendar.set(Calendar.MONTH, DateTimeUtils.createGregorianCalendar().get(Calendar.MONTH));
         resultCalendar.clear(Calendar.DAY_OF_YEAR);
         resultCalendar.clear(Calendar.DAY_OF_WEEK);
         resultCalendar.clear(Calendar.DAY_OF_WEEK_IN_MONTH);

h2/src/main/org/h2/util/ToDateTokenizer.java

@@ -194,7 +194,7 @@ class ToDateTokenizer {
                 result.set(Calendar.YEAR, dateNr);
                 break;
             case RR:
-                Calendar calendar = DateTimeUtils.createCalendar();
+                Calendar calendar = DateTimeUtils.createGregorianCalendar();
                 int cc = calendar.get(Calendar.YEAR) / 100;
                 inputFragmentStr = matchStringOrThrow(PATTERN_TWO_DIGITS,
                         params, formatTokenEnum);

h2/src/main/org/h2/value/ValueTimestamp.java

@@ -10,7 +10,6 @@ import java.sql.Date;
 import java.sql.PreparedStatement;
 import java.sql.SQLException;
 import java.sql.Timestamp;
-import java.util.Calendar;
 import java.util.TimeZone;
 import org.h2.api.ErrorCode;
 import org.h2.engine.Mode;
@@ -217,7 +216,7 @@ public class ValueTimestamp extends Value {
                         tz, year, month, day, hour, minute, (int) second, (int) ms);
                 ms = DateTimeUtils.convertToLocal(
                         new Date(millis),
-                        DateTimeUtils.createCalendar(TimeZone.getTimeZone("UTC")));
+                        DateTimeUtils.createGregorianCalendar(TimeZone.getTimeZone("UTC")));
                 long md = DateTimeUtils.MILLIS_PER_DAY;
                 long absoluteDay = (ms >= 0 ? ms : ms - md + 1) / md;
                 dateValue = DateTimeUtils.dateValueFromAbsoluteDay(absoluteDay);

h2/src/test/org/h2/test/db/TestFunctions.java

@@ -1199,7 +1199,7 @@ public class TestFunctions extends TestBase implements AggregateFunction {
                 "SELECT CURRENT_TIMESTAMP(), " +
                 "TRUNCATE(CURRENT_TIMESTAMP()) FROM dual");
         rs.next();
-        Calendar c = DateTimeUtils.createCalendar();
+        Calendar c = DateTimeUtils.createGregorianCalendar();
         c.setTime(rs.getTimestamp(1));
         c.set(Calendar.HOUR_OF_DAY, 0);
         c.set(Calendar.MINUTE, 0);
@@ -1305,7 +1305,7 @@ public class TestFunctions extends TestBase implements AggregateFunction {
     }
 
     private void testToDate() throws ParseException {
-        final int month = DateTimeUtils.createCalendar().get(Calendar.MONTH);
+        final int month = DateTimeUtils.createGregorianCalendar().get(Calendar.MONTH);
 
         Date date = null;
         date = new SimpleDateFormat("yyyy-MM-dd").parse("1979-11-12");
@@ -1434,7 +1434,7 @@ public class TestFunctions extends TestBase implements AggregateFunction {
     }
 
     private static void setMonth(Date date, int month) {
-        Calendar c = DateTimeUtils.createCalendar();
+        Calendar c = DateTimeUtils.createGregorianCalendar();
         c.setTime(date);
         c.set(Calendar.MONTH, month);
         date.setTime(c.getTimeInMillis());

h2/src/test/org/h2/test/jdbc/TestResultSet.java

@@ -1409,7 +1409,7 @@ public class TestResultSet extends TestBase {
                 "D DATE, T TIME, TS TIMESTAMP)");
         PreparedStatement prep = conn.prepareStatement(
                 "INSERT INTO TEST VALUES(?, ?, ?, ?)");
-        Calendar regular = DateTimeUtils.createCalendar();
+        Calendar regular = DateTimeUtils.createGregorianCalendar();
         Calendar other = null;
         // search a locale that has a _different_ raw offset
         long testTime = java.sql.Date.valueOf("2001-02-03").getTime();
@@ -1422,7 +1422,7 @@ public class TestResultSet extends TestBase {
             if (rawOffsetDiff != 0 && rawOffsetDiff != 1000 * 60 * 60 * 24) {
                 if (regular.getTimeZone().getOffset(testTime) !=
                         zone.getOffset(testTime)) {
-                    other = DateTimeUtils.createCalendar(zone);
+                    other = DateTimeUtils.createGregorianCalendar(zone);
                     break;
                 }
             }

h2/src/test/org/h2/test/synth/TestCrashAPI.java

@@ -486,7 +486,7 @@ public class TestCrashAPI extends TestBase implements Runnable {
             // TODO should use generated savepoints
             return null;
         } else if (type == Calendar.class) {
-            return DateTimeUtils.createCalendar();
+            return DateTimeUtils.createGregorianCalendar();
         } else if (type == java.net.URL.class) {
             return null;
         } else if (type == java.math.BigDecimal.class) {

h2/src/test/org/h2/test/unit/TestDate.java

@@ -352,7 +352,7 @@ public class TestDate extends TestBase {
     }
 
     private void testValidDate() {
-        Calendar c = DateTimeUtils.createCalendar(TimeZone.getTimeZone("UTC"));
+        Calendar c = DateTimeUtils.createGregorianCalendar(TimeZone.getTimeZone("UTC"));
         c.setLenient(false);
         for (int y = -2000; y < 3000; y++) {
             for (int m = -3; m <= 14; m++) {
@@ -467,9 +467,9 @@ public class TestDate extends TestBase {
         assertEquals("19999-08-07", d2.getString());
         assertEquals("13:14:15.16", t2.getString());
         ValueTimestamp ts1a = DateTimeUtils.convertTimestamp(
-                ts1.getTimestamp(), DateTimeUtils.createCalendar());
+                ts1.getTimestamp(), DateTimeUtils.createGregorianCalendar());
         ValueTimestamp ts2a = DateTimeUtils.convertTimestamp(
-                ts2.getTimestamp(), DateTimeUtils.createCalendar());
+                ts2.getTimestamp(), DateTimeUtils.createGregorianCalendar());
         assertEquals("-999-08-07 13:14:15.16", ts1a.getString());
         assertEquals("19999-08-07 13:14:15.16", ts2a.getString());