Add and use fast DateTimeUtils.absoluteDayFromYear()

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

@@ -744,8 +744,7 @@ public class DateTimeUtils {
      * @return number of day in year
      */
     public static int getDayOfYear(long dateValue) {
-        int year = yearFromDateValue(dateValue);
-        return (int) (absoluteDayFromDateValue(dateValue) - absoluteDayFromDateValue(dateValue(year, 1, 1))) + 1;
+        return (int) (absoluteDayFromDateValue(dateValue) - absoluteDayFromYear(yearFromDateValue(dateValue))) + 1;
     }
 
     /**
@@ -825,7 +824,7 @@ public class DateTimeUtils {
     }
 
     private static long getWeekOfYearBase(int year, int firstDayOfWeek, int minimalDaysInFirstWeek) {
-        long first = absoluteDayFromDateValue(dateValue(year, 1, 1));
+        long first = absoluteDayFromYear(year);
         int daysInFirstWeek = 8 - getDayOfWeekFromAbsolute(first, firstDayOfWeek);
         long base = first + daysInFirstWeek;
         if (daysInFirstWeek >= minimalDaysInFirstWeek) {
@@ -1230,6 +1229,26 @@ public class DateTimeUtils {
         return ValueTimestampTimeZone.fromDateValueAndNanos(dateValue, timeNanos, (short) offsetMins);
     }
 
+    /**
+     * Calculate the absolute day for a January, 1 of the specified year.
+     *
+     * @param year
+     *            the year
+     * @return the absolute day
+     */
+    public static long absoluteDayFromYear(long year) {
+        year--;
+        long a = ((year * 2922L) >> 3) - 719_177;
+        if (year < 1582) {
+            // Julian calendar
+            a += 13;
+        } else if (year < 1900 || year > 2099) {
+            // Gregorian calendar (slow mode)
+            a += (year / 400) - (year / 100) + 15;
+        }
+        return a;
+    }
+
     /**
      * Calculate the absolute day from an encoded date value.
      *

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

@@ -91,8 +91,7 @@ public class ToDateParser {
             }
             if (doyValid) {
                 dateValue = DateTimeUtils.dateValueFromAbsoluteDay(
-                        DateTimeUtils.absoluteDayFromDateValue(DateTimeUtils.dateValue(year, 1, 1))
-                        + dayOfYear - 1);
+                        DateTimeUtils.absoluteDayFromYear(year) + dayOfYear - 1);
             } else {
                 int month = this.month;
                 if (month == 0) {

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

@@ -371,6 +371,9 @@ public class TestDate extends TestBase {
                     if (abs != next && next != Long.MIN_VALUE) {
                         assertEquals(abs, next);
                     }
+                    if (m == 1 && d == 1) {
+                        assertEquals(abs, DateTimeUtils.absoluteDayFromYear(y));
+                    }
                     next = abs + 1;
                     long d2 = DateTimeUtils.dateValueFromAbsoluteDay(abs);
                     assertEquals(date, d2);