Fix OffsetDateTime conversion for pre-Gregorian dates (#2568)

* Fix OffsetDateTime conversion for pre-Gregorian dates

* Formatting changes

* Removed unused import

src/main/java/microsoft/sql/DateTimeOffset.java

@@ -5,6 +5,8 @@
 
 package microsoft.sql;
 
+import java.time.OffsetDateTime;
+import java.time.ZoneOffset;
 import java.util.Calendar;
 import java.util.Locale;
 import java.util.TimeZone;
@@ -190,7 +192,6 @@ public String toString() {
                                                                    .substring(2), // -> "123456"
                                                            formattedOffset);
         }
-
         return result;
     }
 
@@ -257,12 +258,32 @@ public java.sql.Timestamp getTimestamp() {
      * @return OffsetDateTime equivalent to this DateTimeOffset object.
      */
     public java.time.OffsetDateTime getOffsetDateTime() {
-        java.time.ZoneOffset zoneOffset = java.time.ZoneOffset.ofTotalSeconds(60 * minutesOffset);
-        java.time.LocalDateTime localDateTime = java.time.LocalDateTime.ofEpochSecond(utcMillis / 1000, nanos,
-                zoneOffset);
-        return java.time.OffsetDateTime.of(localDateTime, zoneOffset);
+        // Format the offset as +hh:mm or -hh:mm. Zero offset is formatted as +00:00.
+        String formattedOffset = (minutesOffset < 0) ?
+                String.format(Locale.US, "-%1$02d:%2$02d", -minutesOffset / 60, -minutesOffset % 60) :
+                    String.format(Locale.US, "+%1$02d:%2$02d", minutesOffset / 60, minutesOffset % 60);
+
+        // Create a Calendar instance with the time zone set to GMT plus the formatted offset
+        Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("GMT" + formattedOffset), Locale.US);
+        // Initialize the calendar with the UTC milliseconds value
+        calendar.setTimeInMillis(utcMillis);
+
+        // Extract the date and time components from the calendar
+        int year = calendar.get(Calendar.YEAR);
+        int month = calendar.get(Calendar.MONTH) + 1; // Calendar.MONTH is zero-based
+        int day = calendar.get(Calendar.DAY_OF_MONTH);
+        int hour = calendar.get(Calendar.HOUR_OF_DAY);
+        int minute = calendar.get(Calendar.MINUTE);
+        int second = calendar.get(Calendar.SECOND);
+
+        // Create the ZoneOffset from the minutesOffset
+        ZoneOffset offset = ZoneOffset.ofTotalSeconds(minutesOffset * 60);
+
+        // Create and return the OffsetDateTime
+        return OffsetDateTime.of(year, month, day, hour, minute, second, nanos, offset);
     }
-
+
+
     /**
      * Returns this DateTimeOffset object's offset value.
      *

src/test/java/com/microsoft/sqlserver/jdbc/datatypes/DataTypesTest.java

@@ -1945,6 +1945,34 @@ public void testDateTimeOffsetValueOfOffsetDateTime() throws Exception {
         assertEquals(expected, DateTimeOffset.valueOf(roundUp).getOffsetDateTime());
         assertEquals(expected, DateTimeOffset.valueOf(roundDown).getOffsetDateTime());
     }
+
+    @Test
+    public void testPreGregorianDateTime() throws Exception {
+        try (Connection conn = getConnection();
+                Statement stmt = conn.createStatement(ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_UPDATABLE);) {
+
+            conn.setAutoCommit(false);
+            TestUtils.dropTableIfExists(escapedTableName, stmt);
+
+            stmt.executeUpdate("CREATE TABLE " + escapedTableName + " (dob datetimeoffset(7) null)");
+            stmt.executeUpdate("INSERT INTO " + escapedTableName + " VALUES ('1500-12-16 00:00:00.0000000+08:00')");
+            stmt.executeUpdate("INSERT INTO " + escapedTableName + " VALUES ('1400-09-27 09:30:00.0000000+08:00')");
+            stmt.executeUpdate("INSERT INTO " + escapedTableName + " VALUES ('2024-12-16 23:40:00.0000000+08:00')");
+
+            try (ResultSet rs = stmt.executeQuery("select dob from " + escapedTableName + " order by dob")) {
+                while (rs.next()) {
+                    String strDateTimeOffset = rs.getString(1).substring(0, 10);
+                    DateTimeOffset objDateTimeOffset = (DateTimeOffset) rs.getObject(1);
+                    OffsetDateTime objOffsetDateTime = objDateTimeOffset.getOffsetDateTime();
+
+                    String strOffsetDateTime = objOffsetDateTime.toString().substring(0, 10);
+                    assertEquals(strDateTimeOffset, strOffsetDateTime, "Mismatch found in DateTimeOffset : "
+                            + objDateTimeOffset + " and OffsetDateTime : " + objOffsetDateTime);
+                }
+            }
+            TestUtils.dropTableIfExists(escapedTableName, stmt);
+        }
+    }
 
     static LocalDateTime getUnstorableValue() throws Exception {
         ZoneId systemTimezone = ZoneId.systemDefault();