diff --git a/src/docs/asciidoc/release_notes.adoc b/src/docs/asciidoc/release_notes.adoc
index 50c7f1099..486d3006c 100644
--- a/src/docs/asciidoc/release_notes.adoc
+++ b/src/docs/asciidoc/release_notes.adoc
@@ -41,6 +41,7 @@ This may affect custom protocol implementations extending `AbstractWireOperation
 This change also improves performance of `updateRow()`, `insertRow()`, `deleteRow()` and `refreshRow()`.
 The best row identifier or `RDB$DB_KEY` were detected _each time_ when calling `updateRow()`, `insertRow()`, `deleteRow()`, or `refreshRow()`.
 This has been improved so this detection is done once, and in a way that non-updatable result sets can now be downgraded to `CONCUR_READ_ONLY` instead of throwing an exception when performing the modification.
+* Fixed: Use of offset timezone names (e.g. `+05:00`) for `sessionTimeZone` would result in a warning being logged, and an incorrect conversion applied (in UTC instead of the offset) when using the legacy time types -- backported from Jaybird 6 (https://github.com/FirebirdSQL/jaybird/issues/787[#787])
 * ...
 
 [#jaybird-5-0-3-changelog]
diff --git a/src/main/org/firebirdsql/gds/impl/GDSHelper.java b/src/main/org/firebirdsql/gds/impl/GDSHelper.java
index f3ef959f4..62d009a93 100644
--- a/src/main/org/firebirdsql/gds/impl/GDSHelper.java
+++ b/src/main/org/firebirdsql/gds/impl/GDSHelper.java
@@ -31,6 +31,8 @@
 
 import java.sql.SQLException;
 import java.util.TimeZone;
+import java.util.function.Predicate;
+import java.util.regex.Pattern;
 
 import static java.util.Objects.requireNonNull;
 import static org.firebirdsql.jaybird.props.PropertyConstants.SESSION_TIME_ZONE_SERVER;
@@ -40,6 +42,9 @@
  */
 public final class GDSHelper {
 
+    private static final Predicate<String> OFFSET_ZONE_NAME_PREDICATE =
+            Pattern.compile("[+-]\\d{2}:\\d{2}").asMatchPredicate();
+
     /**
      * @deprecated will be removed in Jaybird 6, use {@link org.firebirdsql.jaybird.props.PropertyConstants#DEFAULT_BLOB_BUFFER_SIZE}
      */
@@ -268,7 +273,7 @@ private TimeZone initSessionTimeZone() {
         if (sessionTimeZoneName == null || SESSION_TIME_ZONE_SERVER.equalsIgnoreCase(sessionTimeZoneName)) {
             return sessionTimeZone = TimeZone.getDefault();
         }
-        TimeZone timeZone = TimeZone.getTimeZone(sessionTimeZoneName);
+        TimeZone timeZone = getTimeZone(sessionTimeZoneName);
         if ("GMT".equals(timeZone.getID()) && !"GMT".equalsIgnoreCase(sessionTimeZoneName)) {
             LoggerFactory.getLogger(getClass()).warnf("TimeZone fallback to GMT from %s; possible cause: value of "
                     + "sessionTimeZone unknown in Java. Time and Timestamp values may yield unexpected values. "
@@ -277,6 +282,13 @@ private TimeZone initSessionTimeZone() {
         return sessionTimeZone = timeZone;
     }
 
+    private static TimeZone getTimeZone(String timeZoneName) {
+        if (OFFSET_ZONE_NAME_PREDICATE.test(timeZoneName)) {
+            timeZoneName = "GMT" + timeZoneName;
+        }
+        return TimeZone.getTimeZone(timeZoneName);
+    }
+
     /**
      * @see FbAttachment#withLock() 
      */
diff --git a/src/test/org/firebirdsql/jdbc/SessionTimeZoneTest.java b/src/test/org/firebirdsql/jdbc/SessionTimeZoneTest.java
index ff1653a96..8a593aa76 100644
--- a/src/test/org/firebirdsql/jdbc/SessionTimeZoneTest.java
+++ b/src/test/org/firebirdsql/jdbc/SessionTimeZoneTest.java
@@ -20,11 +20,14 @@
 
 import org.firebirdsql.common.extension.UsesDatabaseExtension;
 import org.firebirdsql.gds.ISCConstants;
+import org.firebirdsql.jaybird.props.PropertyNames;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.RegisterExtension;
 
 import java.sql.*;
 import java.text.SimpleDateFormat;
+import java.time.LocalDateTime;
+import java.time.temporal.ChronoUnit;
 import java.util.Date;
 import java.util.Properties;
 import java.util.TimeZone;
@@ -36,6 +39,7 @@
 import static org.hamcrest.CoreMatchers.startsWith;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.junit.jupiter.api.Assumptions.assumeTrue;
@@ -111,6 +115,34 @@ void errorOnInvalidTimeZoneName() {
                 fbMessageStartsWith(ISCConstants.isc_invalid_timezone_region, "does_not_exist")));
     }
 
+
+    /**
+     * Rationale: Firebird expects offset name {@code [+-]HH:MM}, while Java expects {@code GMT[+-]HH:MM}.
+     */
+    @Test
+    void verifyOffsetTimeZoneBehaviour() throws Exception {
+        final String firebirdZoneName = "+05:17";
+        Properties props = getDefaultPropertiesForConnection();
+        props.setProperty(PropertyNames.sessionTimeZone, firebirdZoneName);
+        try (Connection connection = DriverManager.getConnection(getUrl(), props);
+             Statement stmt = connection.createStatement();
+             ResultSet rs = stmt.executeQuery(
+                     "select\n" +
+                     "  rdb$get_context('SYSTEM', 'SESSION_TIMEZONE') as TZ_NAME,\n" +
+                     "  localtimestamp as LOCAL_TS\n" +
+                     "from RDB$DATABASE")) {
+            assertTrue(rs.next(), "expected a row");
+            assertEquals(firebirdZoneName, rs.getString(1));
+            Timestamp timestampValue = rs.getTimestamp(2);
+            assertEquals((double) System.currentTimeMillis(), timestampValue.getTime(), 1000,
+                    "Unexpected value with offset time zone");
+
+            assertNotEquals(LocalDateTime.now().truncatedTo(ChronoUnit.MINUTES),
+                    rs.getObject(2, LocalDateTime.class).truncatedTo(ChronoUnit.MINUTES),
+                    "sanity check: expected a value not equal to the current default zone");
+        }
+    }
+
     @SuppressWarnings("SameParameterValue")
     private void checkForTimeZone(String zoneName, String timeValue, String expectedLocal, String expectedZonedString)
             throws SQLException {