TIME STAMP PROBLEM WITH ION8650 TO MICROSCADA

We are using around 4 ION meter in the one substation. In the ION meter(ION-8650) the time is synchronized via IRIG-B(Reason GPS RT-430). We are getting the analogue value correctly and updating in SCADA, But the problem is the whenever the analogue is changing the corresponding time is not getting changed in our system. The meter is synchronized with time. I dont know exactly the problem. In CET whenever the analogue value is changing the time is not changing