Improve GT06 timezone handling

1 files changed, 12 insertions, 19 deletions

diff --git a/src/main/java/org/traccar/protocol/Gt06ProtocolDecoder.java b/src/main/java/org/traccar/protocol/Gt06ProtocolDecoder.java
index cf7cd12d3..7ee47dd86 100644
--- a/src/main/java/org/traccar/protocol/Gt06ProtocolDecoder.java
+++ b/src/main/java/org/traccar/protocol/Gt06ProtocolDecoder.java
@@ -480,28 +480,21 @@ public class Gt06ProtocolDecoder extends BaseProtocolDecoder {
             buf.readUnsignedShort(); // type
 
             deviceSession = getDeviceSession(channel, remoteAddress, imei);
-            if (deviceSession != null && !deviceSession.contains(DeviceSession.KEY_TIMEZONE)) {
-                deviceSession.set(DeviceSession.KEY_TIMEZONE, getTimeZone(deviceSession.getDeviceId()));
-            }
-
-            if (dataLength > 10) {
-                int extensionBits = buf.readUnsignedShort();
-                int hours = (extensionBits >> 4) / 100;
-                int minutes = (extensionBits >> 4) % 100;
-                int offset = (hours * 60 + minutes) * 60;
-                if ((extensionBits & 0x8) != 0) {
-                    offset = -offset;
-                }
-                if (deviceSession != null) {
-                    TimeZone timeZone = deviceSession.get(DeviceSession.KEY_TIMEZONE);
-                    if (timeZone.getRawOffset() == 0) {
-                        timeZone.setRawOffset(offset * 1000);
-                        deviceSession.set(DeviceSession.KEY_TIMEZONE, timeZone);
+            if (deviceSession != null) {
+                TimeZone timeZone = getTimeZone(deviceSession.getDeviceId(), null);
+                if (timeZone == null && dataLength > 10) {
+                    int extensionBits = buf.readUnsignedShort();
+                    int hours = (extensionBits >> 4) / 100;
+                    int minutes = (extensionBits >> 4) % 100;
+                    int offset = (hours * 60 + minutes) * 60;
+                    if ((extensionBits & 0x8) != 0) {
+                        offset = -offset;
                     }
+                    timeZone = TimeZone.getTimeZone("UTC");
+                    timeZone.setRawOffset(offset * 1000);
                 }
-            }
+                deviceSession.set(DeviceSession.KEY_TIMEZONE, timeZone);
 
-            if (deviceSession != null) {
                 sendResponse(channel, false, type, buf.getShort(buf.writerIndex() - 6), null);
             }